I had that happen once. I was "exercising" my SRT by accelerating hard off a highway entrance ramp. I put it to the floor, the car downshifted twice, and took off. I cut over to the far left lane and then lifted as my speed was well over 80 mph. At the moment I lifted, the transmission shifted with a big "clunk" and I quickly realized the engine was revving freely. I drifted back across the highway (in front of all of the people I'd just dusted who, I'm sure, were enjoying my misfortune) and coasted up the exit ramp into a gas station. I shut off the car and let it sit for 30 secs. I started it up and it was fine. I manually shifted through all the gears on my leisurely drive home with no problems.

Since then, I've punched the throttle once or twice but haven't had that problem again.