Unfortunately that's the thing with people who battle mental illness... they can be doing wonderfully and seem to be at their best for a good long time, and then have a sudden, unexplainable breakdown. There usually aren't any visible signs whatsoever, it just happens.
I hope that Peter is, or will be, all right, and that he is able to "get back on his feet" again very soon (if he has indeed had some sort of breakdown, as suggested by the statements that he's been "found" and is being "taken care of").