Rated 2 out of 5 stars
Unfortunately there's no possibility to recover text if browser crashes and you have to re-login on a website. The add-on always uses the same text file for a webpage and deletes its content as soon as you navigate to a different page.This review is for a previous version of the add-on (1.3.1).
You're sort of right.
When IAT creates a file, it tells Firefox to delete it on close. Depending on the version of Firefox, it may actually delete those on startup. I suspect that what happened is the file got marked as delete-on-close before it crashed and when Firefox started up it cleaned all those files up.
IAT 2.0 (I'm working on it now) will be cross browser and will manage file expiration differently.