Comment 1 for bug 582879

I can confirm this bug in 9.10. I could be fixed in 10.04 or in the dev distro branch. A back port would be nice. There coudl be an upstream patch, plugin or scirpt that could solve the problem.
Possilbe work around solutions:
Hide db files, or hints through renaming or moving of special files to get the photos to merge.
Write a script that merges the two databases and directory trees.
Change the directory f-spot uses in preferences to the old, mobile, or smaller database. If the old database and photos come up then export them then switch back to the main database and re-import.

Other ideas:
Photos from many cameras and certainly most d-slrs often have serialized numbers which could be used along with file fingerprints to identify a new source location automagically. This should be a feature of the main program but it could be a plug-in using createdb and locate to index and find photos and heal the database when photos exist as only data and thumbnails. The same plugin could offer another view to see all photos on the system or in specified file trees without interacting with the database.