I sure hope they're caught and directed to reimburse the county, and provide some serious sweat equity. Being from the neighboring county, I agree that it was most likely perpetrated by spoiled rich kids. More typically they trash a private residence in the course of an unsupervised party, but this kind of behavior pops up from time to time.
I agree with you that they should be caught and held accountable. I a wary of forcing them to reimburse the county though. That has turned into a real boondogle for counties. Public works and expensive labor to build them mean that this restroom probably had a bunch of over-priced extras and cost a fortune.
Counties and townships have tried to force people "at fault" in accidents or for fires to pay the cost of police or fire services too. Once again, I understand the desire to hold people to account but the government offloads a bunch of overpriced, union rate costs onto the citizens in doing so. The cost imposed is much, much higher than it should be.