I believe McCoy went back the next day...
Remember these critical factors concerning McCoy vs Cooper:
1) McCoy successfully landed in his intended LZ. Cooper likely did not.
2) McCoy had no immediate need to worry about being pegged as the hijacker. Cooper, on the other hand, left his tie and tie clip onboard. He would have certainly been concerned about that fact.
3) McCoy got caught because he was reckless--talked about it in advance and hid the money in his closet. Cooper, on the other hand, got away. Put another way, Richard Floyd McCoy was no DB Cooper.