OP has asked Clemson if such a letter was received. If yes, there will probably be a fair hearing, a final chance to explain. If the letter was not received, if they can’t find it in their files, then Clemson is unlikely to raise any issue. OP probably handled this awkward situation as well as could be expected, and now the ball is in Clemson’s court.
“All that is required for evil to triumph is for good men to do nothing.”