Automatic Transmission Revving High 4th to 5th

I was trying to pull a small lawn tractor out of a neighbors ditch and lost all throttle. I drove the truck and had it rev very high 4500-5500 rpms from 4th to 5th gear (Slipping). In speaking with a few people, it was suggested to put in a new valve body with solenoids in which I did. Unfortunately, the problem remained unchanged. I took it to a reputable transmission shop and was told that the clutches were worn and that it was recommended to have a full rebuild. Since my truck has 214k hwy miles, I opted to do so. After paying $2314.14, I am still having the same issue, but only if the truck is cold? I tried the two calibration steps, to no avail. I plan on bringing the truck back to the shop tomorrow, but very curious if someone has a clue as to what could be going on with it? I never had any issues, with the trucks shifting from 4th to 5th until I tried doing a good deed for a neighbor? Its like it cannot find 5th gear momentarily? Could a Throttle Position Sensor cause this?