The hard drive on which I had my entire library of movies/shows was recently stolen The laptop that had the Plex app installed was also taken. Is there somewhere in my online account that has some sort of back-up or just a list of the titles I had in the library?
I know this is a pretty unfortunate and unlikely situation from which to try to recover, but even a list of the titles I had would be something I could start to rebuild.
Unfortunately (for your situation), there is no such backup in Plex’s systems. We do not collect information as to what your library contains.
If you have a backup of your database anywhere or used some third-party tool which enumerates your library (such as TauTulli), they you can likely get the list from there.