I think the distinction is pretty clear. When a rift is formed by placing a bag of holding within a portable hole, both items are sucked into the Astral Plane but are not destroyed (and nor are the contents), allowing for the possibility of recovery at a later date.
The rift is only open for an instant, and closes before any other items or creatures can pass through.
"bag and hole alike are sucked into the void and forever lost"
Pretty sure that means you can't get your bag back
Discern Location
School divination; Level cleric 8, sorcerer/wizard 8
Casting Time 10 minutes
Components V, S, DF
Range unlimited
Target one creature or object
Duration instantaneous
Saving Throw none; Spell Resistance no
A discern location spell is among the most powerful means of locating creatures or objects. Nothing short of a mind blank spell or the direct intervention of a deity keeps you from learning the exact location of a single individual or object. Discern location circumvents normal means of protection from scrying or location. The spell reveals the name of the creature or object's location (place, name, business name, building name, or the like), community, county (or similar political division), country, continent, and the plane of existence where the target lies.
To find a creature with the spell, you must have seen the creature or have some item that once belonged to it. To find an object, you must have touched it at least once.
To me "forever lost" means "requires a quest to find again", just like any other "forever lost" item. It hasn't been destroyed, otherwise the item descriptions would say so, and the above spell is pretty darned handy for finding things that still exist.