You were an imposter, that's slaughtered numerous crewmates on various occasions and locations. You were never caught, never found, until you went to the original Skeld to hide away from the world. It was lost in space, eventually you froze up, not dying however.

A year later the "Skeld II" passes by the wreckage, and looks for you. The crew steps aboard, shining their flashlight around the ship, landing on you. Still frozen. Presumably dead.

Red, inspecting your appearance: "There he is. We found him."