[He holds the communicator steady as he walks--yes, walking rather than flying for now--looking thoughtful.] I couldn't say why, but I have an impression they might have been trapped, themselves. Which makes their disappearance very ominous, indeed.

The Machine being here doesn't shed much light, either, though. Someone has to have built it. It's all very odd; I feel as though it's a puzzle with half the pieces missing.