You could restore the profile folder backup to a convenient location, then start the profile manager, create a new profile and point it to the restored profile folder, then start Thunderbird using that profile. See http://kb.mozillazine.org/Profile_Manager#Mac_OS_X for details.

If you want to restore the backup to its original location, you'll have to rename it to something else because your current profile folder is still using the same name as the backup. For example, you could rename it from xxxxxxxx.default to xxxxxxxx.default-old-pop then move it to the original location.

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Not sure if you mean deleted the account from Account Settings or whether you completely deleted the actual profile. If you did not delete the profile itself..... When you remove a pop mail account, it does not mean it has disappeared from the profile folders. Check to see if those files still exist and simply copy the mbox files into Local Folders.

Suggest you try this: In Thunderbird: Help > Troubleshooting Information click on 'Open Finder' button

This should open a window showing contents of profile name folder.

Exit Thunderbird now - this is important.

Click on 'Mail' folder. You should see the 'pop' mail account name folder and 'Local Folders' folder.

Click on pop mail account folder. Copy all the mbox files - they will have same name as folders but no extension and they contain emails. Not .msf files as they are only index files. If you see .sbd folders then you had subfolders, open those .sbd folders and you may see more mbox files. Paste those mbox files into the 'Local Folders' mail account folder.

Start Thunderbird

You should see new folders appear under 'Local Folders' mail account.