Enough facts, time for speculation:
- My wheel is haunted.
- I've been right all along, the CIA, FBI, and NSA are after me, and they've got covert black ops guys breaking my spokes. The tin foil hat is going back on my head, thank you.
- I don't know if it was the same spoke (I didn't mark its location first time), but if it was, maybe there's some kind of deformation in the hub's spoke hole that's weakening the spoke, and the deformation is such that it continues to exert force on the spoke even after it's not being ridden.
- Maybe the wheel has just reached the age at which it has multiple failures, unrelated to each other.
- Maybe severe temperature change stressed the spokes beyond their tolerance. But in both cases, the bike was left in its ambient riding temperature.
Explanations 4 and 5 don't explain the main mystery -- how a wheel at rest, with spokes at minimum stress, breaks.
Anyway, I'm taking precautions (beyond the usual plastic surgery and fake identity). I've marked the location of the last broken spoke. We'll see what happens over the next weeks.
I bet you can hardly wait, huh?! Sort of like 24 or Lost, huh?