I know for a fact that an IDOC with vendors in it will not drop, but will go to OSI ownership. That is intended so that vendor owners can have extra time to gather up their vendor items/gold. This happened to me. Also witnessed such action on several homes that were idoc, then went to OSI right before my eyes.
Basically, the house will continue to "refresh" with "Demolition Pending" and OSI ownership for about 2 weeks (9 days plus some vendor contract thing dictates the timing here - not sure exactly though on this). Then, regardless of vendors being in the house or not, the house will be dropped without any other status changes.
I suspect that the vendors have to go *poof* in order for the OSI owner to drop the house, so, if the vendor owners don't care, they just go *poof*.
Right now am watching a couple of properties that flipped to OSI ownership with vendors. Just... waiting.