I actually don't miss the disposition mini game at all. I rarely did it in Oblivion. I felt the whole thing was kind of silly.

Adding more gold to vendors is a speech perk.

I tried to place a flawless garnet at a wayshrine of Dibella.
I figured the Godess of beauty would appreciate such an offering.

But a pilgrim gave it back to me :/
"Here, I think you lost this."

I also got handed back a BOWL that i thrown away intentionally... so yes, NPCs give you back things if they find it.