I have notice the same issue. After takeoff from Mun, my vessel is in orbit around Mun without orbit line.
After reading @LameLefty post I have confirm vessel status in Tracking Station is “landed,”.
I have a save game available if it can help the DEVs team.
Just in case there is a relation, this It may help to mention that the command pod of this vessel explode if I try to EVA.