Does he have a mobile phone? Some mobile phone services can be used & show up in a wifi service option (I think, I do not really understand how it works.) The system might have detected another service (even if only temporary) & switched. Perhaps he might have been trying to hook his mobile up to the local wifi or vice-versa. Wild guesses on my part.
I'm basing my suggestion on a friend's macbook pro & iphone which apparently shows two other wifi options to connect through (due to the iphone), outside of the hard-wired LAN.
Edit: Just remembered I think they said the iPhone scans for wifi options.

Sleepless or one of the others no doubt understands wifi better.