Could it be that our old friend Murphy paid you a visit?
He did pay me a few visits and I mixed up the films sendind the unexposed rolls for developing, instead of the exposed ones.
X-ray damage seems so out of the question, since such high levels that completely fog the film would also do quite some damage to humans. In addition you would also not see the edge imprints, which in your case are visible.
BTW, if you did send the unexposed ones, be on the lookout for some rolls with double-exposures