"Wayne" writes:

I can't imagine who else would break in and not take anything.

A thief who didn't find anything interesting after he broke in? A
bored kid breaking stuff for kicks? Maybe you forgot to lock it, or
it came loose (airplane locks are usually too reliable), and the door
came open....

It seems really unlikely and FBO is going to break into an airplane
just to get your name! Most everybody knows how to look up owner
names and addresses from the online FAA database.