I'm talking about flashing to a TDB firmware hack and then flashing back to the original firmware...could they tell if you had to return it?
I think you're missing something. If you choose to flash to unsupported firmware, you are choosing to void your warranty, and giving up the right to return your drive. If you can't afford to lose it, then leave it alone.
But you didn't answer the question. If you flash back to the orginial firmware can they tell?