Floridafan sounds like things are good to go with your son and that's great. Do you mind telling us exactly what the doctor said in his case and what he had him do?
jkkmom don't be afraid to get a second opinion on his elbow. Something I'm not sure if I follow in your post - did the trainer make an appointment with your ortho doctor or another one he / she may know?
The pitching an hour later wasn't the best thing in the world and I'm willing to bet it was a fairly cold day. He probably got cold and tight and his arm didn't respond well.
Make sure he sticks with the rehab plan all the way. Let us know how things are going.