My guess is she was murdered and the boyfriend would have to be the number one suspect at this point.
90% of the time, the victim knew the perp. 90% of that time, it’s the spouse or boyfriend.
Waiting for 11 hours is pretty hard to explain, if during that 11 hours he received some sort of notification that she was kidnapped.
I bet the police will be looking into him for exactly that. I wonder how many ransom kidnappings there are in the U.S. every year.