I was wondering the same thing. Perhaps our fearless leader, Chris, could get some intel on this. Although, he is probably getting ready for his radio gig.
Probably just getting rest. It's not that uncommon in wrestling to have backups wrestle even if the starter is healthy. Thompson wrestled tough in the midlands and he's going to be the starter next year. Give him the experience of big time duals before he's thrust into the spotlight.
Does anyone know if Zabriskie even suited up? Perhaps Varner's pin was enough to give Jackson confidence in the meet to send Thompson out there as a last minute decision.