The jetway goes away when I close my doors and boarding is complete. Then I request pushback, and as the pushback truck comes, the jetway re-attaches itself. That occurred just now at gate E14 in FSX:Steam.
One thing also the pushback option for some gates such as E are not right, it should push you perpendicular to taxiway RB on the ramp taxi line, not push back all the way onto RB facing either left or right.