A quick search turned up the following abstract indicating that bone mets are more common than one might think in late stage gyn cancers:
I'm guessing a lot of these are asymptomatic while patient is living. Also suspect that it is possible that Ovarian cancers may not demonstrate osteoblastic activity in all cases. Hence, it could be possible metastatic lesions would not appear on bone scan.
Just speculating, as the data I seen with <1% of ovarian cancer present with bone mets came from some pretty prominent centers from 2003-2006. I will try to dig them up again. These were from living patients, and no postmortem.
I wonder how many from which you site were detected premortem?