Tow/haul and transmission issue

When we had our 2006 dodge mega cab 1500 we had a similar problem. It had been many years since I had towed anything and it was our first trip out with the new camper. We were heading to the northern end of New Hampshire. Anyways we stopped to get gas and when we started goin again I forgot to put it in tow haul mode. I realized it when we hit a hill and the transmission began shifting and the RPMs went sky high. Pushed the button and it all came back to normal until we hit the next hill. The truck lost all power wouldn't go over 45 RPMs just sat steady a little over 3000. When I had a good spot to pull off I did. Turned everything off let it settle for a few minutes and then began to check fluids. Everything was good so we waited a bit more took some photos and off we went. Everything worked fine from there on out. Forgot to ask dealership about it when we got back. So the computer thing sounds bout right.