Treat it as a ranged attack with a thrown weapon. That means the non-proficiency would apply for trying to use a weapon you aren't proficient with.
It does return even on a miss.
Melee weapon is a category of things. If it isn't a weapon, and you are trying to use it as one, then it is an improvised weapon. This ability works with things that are weapons, not improvised ones. Weapons are listed as such in equipment chapters of books, or otherwise state that they are a weapon. No throwing bookcases.
Its limited to 30', no range increment is provided, so there is none. Just like a ranged attack, you can try to attack a creature you can't see, such as invisible, but think you know where they are by targeting the square. If you pick the correct square, they still get a 50% total concealment miss chance.
You can attack objects, sure.
The attack occurs when you spend your standard action to do it. I don't know what you mean about the rest of that sentence.
You're overthinking things here. It works like a ranged thrown weapon attack except for the specific ways it states otherwise. It doesn't say anything about proficiency, so you do take any non-proficiency penalties as you normally would if making an attack with that kind of weapon. Don't get hung up on tiny wording issues like "does it return on a miss?". Something that important would be stated explicitly, so we can presume it returns even on a miss. Any game master who rules otherwise is being unreasonable and mean-spirited.
Also, you might want to look at the Accomplished Sneak Attacker feat. Rogue/Wizard was absolutely terrible as a multiclass combo before that feat was released, but now you can use that feat to qualify for the Arcane Trickster prestige class as a Rogue 1/Wizard 3 so it actually works fairly well.
Rule in question: Universalist Wizard ability "Hand of the Apprentice" on page 82 of the Core, bottom left corner of the page:
"Hand of the Apprentice (Su): You cause your melee weapon to fly from your grasp and strike a foe before instantly returning to you. As a standard action, you can make a single attack using a melee weapon at a range of 30 feet. This attack is treated as a ranged attack with a thrown weapon, except that you add your Intelligence modifier on the attack roll instead of your Dexterity modifier (damage still relies on Strength). This ability cannot be used to perform a combat maneuver. You can use this ability a number of times per day equal to 3 + your Intelligence modifier. "OK so the whole proficiency thing boils down to ...
This is an attack power of the school and not a weapon attack. Weapon proficiency does not apply.
Another issue which I'm guessing everyone will laugh about when I mention it but, because of the wording, is open to interpretation.
What happens if you miss? Rule says it instantly returns after striking. So if you miss....you didn't strike....sooooo no return?
Had it stated "...strike at a foe..." then no prob but it don't so?
I assume the obvious that even misses return but still, two letters takes it from arguable to solid.
Striking is this case does not equate to a actually hitting. Even a miss returns the weapon.
I agree that it not being a thrown weapon shouldn't create a penalty for it NOT being a thrown weapon. That just seems to really go against both the spirit and the wording of the ability when it says "You cause your melee weapon to...". I didn't even get the impression there were range penalty issues (didn't occur to me until reading one of the other threads).
It is a ranged power not a thrown weapon, so penalties for throwing do not apply. Penalties for ranged attacks into melee do.
Can it be held by the caster and used as a melee weapon (one or two handed, ability states "grasp" and you can grasp things with both hands)? If it's reasonable to the GM that he could use it as a weapon, then it flies (you can grasp a bookcase with both hands, can you use it as a weapon? not really...if the wizard has a belt of storm giant strength , however...). Personally, I'd put it at some kind of ability modifier to determine if it could be used as a weapon. Say, anything that doesn't produce a -8 in standard melee combat (this is where your proficiencies come in) or more to hit would be considered a melee weapon (not fully familiar with the rules to come up with a notch on the bar but you get the idea) meeting a definition of something usable in melee as a weapon.
The definition of weapon should be of functionality, not intent.
You cannot hold the power. You can hold the weapon you use the power on. It then leaves your grasp to attack. You cannot "ride" it or be pulled along by it. As already mentioned, it does not work for improvised weapons.
The attack occurs at the end of an action (takes one full standard to do, so I'd consider the caster concentrating/preparing/triggering for the full round for it to happen at the end-can't really be disrupted, however) so for those with multiple attacks or whatever else is going on around the wizard, they'll go first (unless they're doing full action maneuvers as well).
Not sure where you got this.
The attack occurs AS the standard action. You can ready the attack if you want. You can move then [ready an] attack. As to what happens with others, unless they cause an attack of opportunity [AoO] or a readied attack to go off, you do nothing during their round. If an AoO is triggered, you cannot use the power as it does not allow that. You can use the weapon you are holding for the AoO if you want.
/cevah
It is a ranged power not a thrown weapon
The rules text says otherwise:
This attack is treated as a ranged attack with a thrown weapon
Now, I do agree that there are no range increment penalties because the Hand of the Apprentice ability explicitly specifies its range. However, for everything else it inherits the normal rules for ranged weapons attacks.