I'm not claustrophobic but I did use to have a very (un)healthy fear of flying, and like you I deplaned one time. In my case it was an MD80 at BOS destined for Amsterdam. Getting off of the plane was embarassing. Delaying the flight for a half hour while they looked for my checked bag was humiliating.
But I got over it with a little time and alot of hard work. I'm sure you can too.