Sometimes when Bob migrates the db to a new host links can get broken.
No-no, I think the reason should be different.
It happened to me twice. I created a page for a new person and an untagged photo of some other person was automatically attributed to it. The other time I created a page for a new movie, and a photo of some actor that wasn't attributed to any movie, was automatically attributed to that new one. In both cases the automatically attributed photos had no connection to the people or the movies they were attributed to. So I think there might be some bug in the system, that sometimes make this kind of things and creates more mistakes.