Would thief let you keep a wild pokemons item?

Question

I could use it on a chansey swarm until I steal a lucky egg! its all comin' together....;)

Answer 1

Yes you can keep items stolen from wild Pokemon, teach Thief to a Banette because it's ability tells you if the enemy has a item and what item it is.

Answer 2

Yes, this is what are Covet and Thief used for:))