To what extent did it delete? Did the icon simply "disappear" or was there a noticeable period when the main folder was deleting?
If the former is true, search for the X-Plane file in the Finder.
If the latter is true, try to get it out of the trash.
If the folder (and its contents) are actually removed from the computer, than you might have to reinstall. If this is true, please reply.