Photo Gallery not seeing Firebird folder structure

I have my images in a Firebird folder hierarchy which seems to be working OK. I am using the Photo Gallery plugin to create portfolios on my site. This was working fine with Firebird for a couple of weeks.

I deactivated Firebird whilst I tried a new Media folder plugin but I didn’t like it and deleted it, then reactivated Firebird. The firebird hierarchy is intact and I can use it fine in Media. But when I try to add an image to a Photo Gallery album using Add Images or Import from Media Library I now only get the very top level of images in Media. I see a folder within that screen that is called imported_from_media_library but when I click on it I just get all my images in no folder structure at all!

I’m wondering if I have accidentally deleted a plugin of some kind that Photo Gallery needs to help it run properly.