Does it sound like any of these? I just did a search for Midis of Billy Joel's Songs.
http://torgo.978.org/~jw/midi/Joel,_Billy/

I had a tune going through my head for years until a friend and I worked it out what it was. Turned out to be a commercial from the early 60's. (Not that I'm that old to remember one ) Don't know how it got in there.

Good luck.

- Brian