Based on the wreck site imagery taken via sidescan sonar, the stern appeared to yaw as it smashed into the ocean floor. One can clearly see on the bottom what appeared to be swivel marks in the mud. If the fairwaters didn't implode from water pressure as the stern sank, as was mentioned they were oil-filled, they were probably projected somewhere outside of the yaw marks.
If the fairwaters were filled with oil, then they would resist crushing. Depending on the type of oil and how well the fairwater kept out the pressure, at some point the oil might start acting as a floatation device and could push the fairwater off.
Perhaps when the stern hit the seafloor, combined with the buoyancy of the oil, it knocked the fairwaters free.
If they did "float off" nearer the surface then they could have landed quite far from the main wreck. Not really plausible, but in theory they could still be floating around today, a few hundred feet under the surface. Not likely, but fun to think about.