If a GM placed them as deeds, the same GM has to convert them back to deeds using the exact same Bioware name and GM avatar name. I suggest you talk to them directly to attempt either this method or to use the GM Furniture Tool, which can be used by any GM.
I can remove them from the database, but I'd like this to be a learning opportunity for the GMs who may have placed them and/or tried to remove them. In reality, it's not really a good idea to use housing deeds for quests, especially when a GM can put down placeables in a way that is more easily destroyed...which would be learning opportunity #2. *smiles*
They did not become part of the module. It doesn't work like that. They're in the database. Guarantee it.
As for your limit, it's possible, but the system just stops loading them at 200. It's technically possible to have more than 200 placeables for any given address.
Don't worry...there's nothing "spooky" going on here.