Taking that kid's PSP may only get him into trouble, unless he has a really good explanation of who gave it to him and that person is willing to cover for him as well. It's ok to trust people with your stuff, but you got to know who is worth trusting and who is not.
This reminds me a bit of a similar thing I had, but it wasnt like this though. I don't usually tell stories about myself here on the forums but I'll make an exception since this is kinda comparable.
Some girl that was in my friend group when I lived in Spain got borrowed two CD's from me, which was fine with me even though that girl kinda irritated me and I wasnt really her friend, she was a best friend of another girl in the group so I just kinda put up with her somehow. My mother suddenly had to leave to Iceland, for reasons I'm not going to explain here, and since it was so sudden I was leaving two months after she did.
The day I was going to leave to Iceland, 3 hours before the plane was going to take off me and my boyfriend were knocking on her door after calling her on the phone and looking for the girl all goddamn day. No sign of her. So I gave up and we didnt have more time for that nonesense anymore since we'd miss the plane if we kept it up.
Some time after that when talking to her best friend on msn she tells me the girl had been -hiding- in her house and didnt open the door when we came looking for my CD's, intentionally to keep them. I wouldnt really give a crap about a pair of CDs but one of them was a gift from my father, who I dont really keep any relationship with or track of and at the time being I had no idea whether he was even alive since I had heard nothing from him in years. So I was pissed off and I didnt really think she'd go so low just to keep two CDs.
When we went back there to visit the friends next summer I went to her house one day without telling anyone about it. The girl was kinda surprised since she didnt expect me to just appear there all of the sudden. I asked her for my CDs and explained to her how one of them was a gift from my father.
Then told her everything I had always thought about her, how she irritated me, that I had no interest in her as a person or a friend and that I did not want to meet up with her while I was in Spain or ever again. At the end I wished her a nice life and left her there crying. Got my CDs and my revenge.
So yeah, my point is, usually truth hurts more than any lie you can tell or any kind of stuff breaking or stealing you can do. Instead of just stealing something back from her I "attacked" her psychologically, and she will probably remember it for a long time.