Hello Mister Ed:
Thank you for posting.
The auto-restore login feature does not store your account name and password. It allows you to bypass the dialog that asks you if you would like to continue working in a file after entering the hibernated state.
A way to accomplish what you desire would be to specify your log in information under File > File Options in FileMaker Pro. You could also script a auto log-in feature using the re-login script step after auto logging in as guest.
Hope that helps.