I'm not an expert on what HTC can do or does do, but I would suppose they can run diagnostics on a bricked phone and get quite a bit of information (depending on what had been done to the phone). If some of the information doesn't match what they expect to find, I would imagine they'd have a pretty good idea of what had been done to the phone.
Mind you, that's a lot of supposition and guessing, but I don't think it's beyond the realm of possibility.