just cuz it's gone doesnt' mean the problem won't come back. Good thing you're taking it to a mechanic. Glad its working out
Big steve if i where you i would still get that looked at. The temp may have been an issue causing slippage, there are quite a few things that could cause the slippage. But the flopping noise sounds like a slipped belt or something along what wasper was saying a possible tear. The shop you took it too will want repeat business from you so it would be in his best interst to ease your worries by putting the car on a lift and showing you the pully. I know i would be taking my car back if i heard anything unsual. But im anal like that.. Good luck and i hope you troubles sort themselves out.
Yup, my beat is on the slipping belt. Either the tension wasn't correct or the belt was misaligned in the grooves of the pulley.