Deleting the password should not have required deleting the account.
To return the file to it's original "Factory Settings":
Open Manage | Security.
Define a new account named "admin". Select the [Full Access] privilege set option. Do not specify a password.
Exit out of Manage | Security and enter "admin" when asked for a full access account, leave the password box empty.
Now go to File Options from the File menu, select "Open With" and specify "admin", but with no password as the way to open this file.
Test and make sure that the file opens with admin and does not ask you for a password. Now return to Manage | Security and return the Guest account to it's original settings if you wish to do so.
PS. It's often not a bad idea to save a back up copy of your file before making major changes to accounts inside Manage | Security. That way, if you accidentally lock yourself out of the file, you can toss that copy and revert to the back up.
Thank you so much Phil. I've wanted to clean up some files like this for a long time.