Motor racing while driving?

This morning as I was in line at Burger King, I was in the drive through on a down hill slant. I noticed the engine running a little rough and when I pulled forward with alittle gas the motor stayed up on RPMs even after I depressed the clutch. Once I got my food and on the road "on level surface" it was still doing the same thing. As I pulled up to a stop, with clutch pushed in or even in neutral the engine would continue to race up around 2 or 2.5 rpms. If I sit for about fifteen seconds it will idle back down. I checked the pedal to see if floormat was sticking. When I got home I opened up the hood and checked the linkage and reved it a few times and it would do the same thing? Thanks for any responce. Could the waiting in line on a slant have done anything?
56k miles
5 speed
5.2L

I just wanted to say that after I let the truck sit for about thirty mins, the problem has stopped. I think just being on a slant for some reason it messed with the sensor or something.