x-ray damage
I'm guessing it WAS x-ray damage - though I have never seen the like. Good rule - NEVER put film in checked baggage! In the last 10 years I have traveled with ISO 100 film to China 3 times, Europe 4 times and other domestic travels. I always let my film be scanned by carry-on TSA or Chinese or Germans and have not suffered a trace of scan damage. In Italy 10 years ago I made two exposures on 4x5 Tmax 100 film pack and put one in checked baggage and the other in for-scan carry on. The film in the checked bag DID show a Zone I fog streak but it could have been printed through. Develope the rest of your film - you have nothing to lose and maybe something to gain!