system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If you are sure that someone stole your wallet and put it in their purse, what would happen to you (legally speaking) if you stole their purse to prove they stole your wallet?
gpt
Provided it was in the purse, or you had reasonable grounds to suspect it was in there.  In the US you have a lot of grounds to do a lot more than that in order to protect your property.  In other places, you would probably have the grounds to, so long as your purpose was only to retrieve your own property.
Legally speaking to steal you must have the intention (mens rea) to permanently deprive the other person of *their* belongings.  It must also be dishonestly, and because this is not, it would not constitute theft, nearly anywhere in the world.