I've never had an engine failure, but once while flying x-country at night I thought I noted a change in the sound of the engine. Careful listening for several minutes didn't reveal any more irregular sounds. Makes you sit up and take very close notice of everything though. I'm sure it was just my mind playing tricks on me to keep me alert.
I have had one comm failure though (if you could call it that). Just after takeoff I was being handed off to the Terminal controller from Tower and the radio went dead. First thing I did was to push the headset plugs firmly into their sockets - thus solving my comm failure.
But I'm glad to see that I didn't panick. I always tell myself, check the simple things first.