serpentine belt, heater/radiator hoses.

When I put in my new heater/radiator hoses, I removed: The battery, Alt, Pwr Steering res., radiator fans, intake elbow+ cia, serpentine belt.

So I put everything back together but an alternator bolt fell and I couldn't find it. I'm assuming it still stuck somewhere since it's not on the ground. I then put my new driving belt on, bled the rad fluid and everything seems ok.

BUT, I took the car for a drive and noticed a vibration in the gas pedal from around 1200rpm to 2000rpms that I couldn't feel before I did all this work.

Any ideas on this one??? Can a bolt stuck somewhere do this?
Finding that sucker will be next to impossible unless I take everything out again.