Greetings, new to the game. Playing career mode. I've a 'space station' built with crew and lab modules, and with cross segments holding RCS and fuel storage tanks. I built a 'tug' and brought it up to the station, the idea was to use it to move parts around during the construction process. It worked quite well, and I left it docked overnight. Today, I resumed my construction project. The tug holds a lot of RCS, and figuring it didn't need fuel, I offloaded what was left to the station holding tanks. I decoupled the tug and waited for it to drift clear for a moment, then switched to Tracking to go pick up the tug and fly it. It was gone. It just disappeared... and with it, the pilot onboard, who is now listed as "Lost". Any idea why?