I asked Gunslinger to wait in stealth by the Rift at the Compound entrance, and did the Foundry and Waterway Facility Quest after that. Upon returning using the Rift, he is nowhere to be found (checked the entrance and the rail car) and the Gunslinger quest does not appear as failed. The save was made in 1.2.0.13. When I load it in 1.2.0.14 I still cannot find the Gunslinger.