There was no sign of them anywhere, so we packed up the camp and spent today travelling toward the facility. We might make it back by tomorrow evening. There's a real sense of dejection. I suggested that we wait to see if they come back, but apparently the policy is to return to the facility if you get separated. I asked how common this kind of thing was, but nobody would give me a straight answer.
A camera was set up in the middle of the camp, and it might be able to shed some light on what happened. It was on a tripod, facing into the cavern. If it was working when they disappeared, it should show us which direction they went, or maybe give us some idea what happened to them. We'll check it when we get back to the facility.