Not sabotage, just incredibly bad luck
Actually, the inner tube has a tiny hole at the valve. Am I ever glad I forced myself to check the tube underwater for escaping air bubbles, else I would not have discovered this until after the front tire would have mysteriously deflated yet again, which would likely have been some night after working late.
I also forced myself to check the tire for embedded glass shards, just in case, and found a whole bunch of them lurking in a small but gaping cut that penetrated all the way through the tire. Another disaster waiting to happen.
The hybrid needed a new tire in the back, so I had bought one, but unfortunately I had bought only one, because for some reason spending about $1200 another bike has made me thrifty with this one. Not a large problem because I literally have a spare tire, one of the originals from when I first replaced both with the Randonneurs, except I seem to have purchased the wrong size inner tubes in Alton this past summer.
I think I might have an old tube with a patchable hole in it, but the hour was getting late, and with my luck I might have found that the cement in my patch kit had gone dry.