All of you make valid points about who trashed the mansion, but I honestly think that the Dr. is trying to swerve us. Think about it:
- Vinny has the motive, and assuming has a mole to give him the information (Nick), but doesn't explain how did he get the dildos or why did he leave Nick's room untouched, that's a huge question mark and would make people suspicious.
- Jocks are a possibility, although it's incredibly stupid for them to incriminate themselves, they have enough problems as it is. There's no explanation of how they knew no one would be at the mansion or why would they leave Nick's room untouched.
Although it's far fetched, I think it's Troy by himself or with someone else (best possibility is Chad, but that's a long shot). Troy has the motive - he hates the Jocks and would love to get revenge on them for kicking him out, he gets information about the mansion somehow (by stalking or a mole) and probably knows about the dildos from his time in the Jocks.