anybody can understand that the goblin is asleep because they exhibit all the signs of being asleep.
the action to wake them up isn't all that different from waking up a creature who is 'naturally' sleeping.so the sequence of events is: you realize your buddy mysteriously fell asleep, possibly you correlate that fact to the enemy witch doing some mumbo-jumbo just before your buddy dropped, in either case you can chose to try to wake up your buddy if you want to - whether or not you suspect supernatural cause for the sleep is irrelevant to the action of trying to wake them up.
given that the game is set in a world where magic is semi-normal, you can't really know whether or not they are permanently sleeping or can be awoken by normal means, but that isn't really different than a normal person who has gone into a non-magical coma: you find out by trying.
No, they do not exhibit all the signs of being asleep, they are put into a "deep magical sleep", it does not say that they exhibit any normal signs of sleeping. For all intents and purposes, you can say they just look unconscious. Since it is supernatural, you couldn't even do a spell craft check to figure out what it is.