I dont think you can get caucht by stealing bitcoins do you know why because bitcoins are not from you they are from everyone who has bitcoins because they are not on your name.
If you use the stolen bitcoin and people can link the spending with you, then you will be caught. It is better to mix it.
Stealing is illegal no one will tolerate that action, and base on the OP statement i think that is not form of stealing he only a lucky person that generate bitcoin address with a free bitcoin balance in the wallet.
How can someone generate already generated address again? if a wallet has balance,it means someone is already using it
To generate already used bitcoin address, the chances are very thin. But in the case of if that collision happens, we must try to conduct the original owner of that bitcoin address, by announcing in this forum. But, taking away that bitcoins must be a kind of stealing only.