AutoCAD Inventor :: Identifying Assembly Context Required Saves

I'm running into issues with some skeleton parts (with the BOMStructure type of "kPhantomBOMStructure"). When these files are manually opened up by themselves and saved, I get an error stating that "<filename> can only be saved in the context of another document which is not currently in memory".

I've seen other people with this problem in the regular Inventor discussion group ("cannot save changes", "save error"), but with no real solution.

What I'd like to be able to do is find out through the APIs which file this needs to be saved with. I'm worried that I wont be able to get this information since Inventor itself won't tell me.