... this time was successful, much appreciated.

I did know I was looking for a "folder" and not a "file",
OK, but other programs - notably Outlook Express and Office Outlook - do store messages in a file, not a folder. You might have been thinking that this program from the same stable acted in a similar way.
... is it safe to delete the original folder that was renamed?
If you're quite happy about the way things are now in the program, you don't need the old folder any longer. However, it would be good to ensure that your store folder is being properly backed up, now that you know where it is.