strange huh?

so i'm driving my gti..you know one of those random i-wanna-take-a-drive-cause-i-just- want-to-type-deals....and made a pit stop for gas.....went to an auto parts store..came out..on the the road again and notice that my car's idling was loping...really erratic...panic ensues.. i retrace my steps..couldn't figure out what the f......EUREKA...wasn't sure if i tightened the gas cap til it clicked...got out did that...what do you know idle went back to norm...didn't realize the ride was that sensitive to such "minor" details