what happens if you drop
Bird pot
Rada book
Malah scroll
Lam essen tome

Good question, i would say that the item is lost to the abyss.

And rightfully so.
If you do a job, and i pay you 100 currency for it, and you then decide to throw the 100 currency on the floor and walk away, then that's your decision and the world is fine with it.

everything you said is wrong and I bet it took effort to get there, congratulations for that

thank you sir

Supposedly, sharing the quest with another character can get you the reward if you missed it the first time, though i'm not sure if that allows to pick up the item itself.
I say "supposedly", since we've seen numerous reports of people being stuck, even on a second shot (Anya quest comes to mind, especially).

On the other hand, there's a tricky way to bypass item destruction upon quest completion.
It's quite a funny thing to still have the item, while not being able to pick it up anymore if you drop it =]

bin

Ive gone into afk games and taken their q drop if mine has bugged out.