I am new here and am just getting to know the forums, but... I know that some guys can put physical pain above physical pleasure. Not saying that sex with you was painful...but here is my example. I produce a more than average amount of body heat. So when my gf and Iget into it, i cannot get too hot or I will start getting sick. Not saying that it was bad for him, but maybe somthing like that arose, i know that there has been at least once i had to stop in the middle because i started getting too hot.
Point 2. You say it was a 1 nighter, meaning that he didn't know you all that well, while most guys wouldn't let that affect them, maybe he had a more than average concience adn felt guilty about not gettign to know you more before getting all intimate. This could also be the reason he hasn't gotten in touch with you since then, maybe embarrassment from stopping mid-run. I know that personally, it would kind of embarrass me if i did it. So the best thing for you to do is give it a day more or two and if he doesn't call back, get in touch with him and see what's up.....
Just my opinion on the whole thing.