A button's good. Probably a good time to add other things too, like a tracker, but paranoia isn't going to help. If something bad happens, he'll own up to it. For now...

"Okay." He folds his arms close to his chest. "How long will it take? 'Til you contact us? And- do you guys know anything, about other places disappearing? Like the train's world? Anything we could get the train to investigate?"

Since, after all: "It really seems to care about finding its missing crew."