It turns out it wasn't Bluetooth - it was one of those proprietary radios with a USB dongle which should be a lot more reliable. But still... it doesn't sound like they had any kind of backup at all. Maybe they just didn't talk about the backups?
wifi dongles aren't exactly bullet proof. For example if you use a cycling turbo trainer with a power meter, a macbook and an ANT+ (2.4ghz) dongle there's a good chance you've had to buy a 6 foot extender cable so get the dongle far enough away from the macbook because something about the macbook itself interferes with the signal. It's a known thing among home training cyclists.
