What's wrong with my 2003 Hyundai Elantra???? Please help!?

I was driving across 800 miles. In the car for 8 hours already, then we hit construction (stop and go). It was terrible. The temp guage didn't show hot and no lights came on but all of a sudden when I hit the gas pedal nothing happened. The care never did die, it kept running it just wouldn't go anywhere. I had a half a tank of gas so that wasn't the problem. I managed to get off the highway and onto a side road. I set there for an hour and a half for help. When help arrived I started the car for him to show him what it was doing and it ran perfect. We got back on the road and completed our trip (another 4 hours). What do you think was wrong with the car as I am headed out again for another road trip and I don't want it to happen again. It hasn't done that again for since and that was 2 months ago.

No dash lights came on or anything and I just replaced the maf sensor so that's not it. Any other suggestionss