-cross posted in Mid-Atlantic forum (oops, there is no Mid Atlantic forum)
Saturday I was riding from Falls Church, VA to DC and Bethesda, MD. Had a quick stop at one of the museums on the Mall. Locked up to a bike rack and went in for about 10 minutes. Unlocked and continued my ride. Noticed that my wireless sensor was clicking - hitting the magnet. Then the brakes felt funny when I stopped using the front brake only. Then I noticed that the front wheel felt funny - making noise, rubbing the brake, etc. I stopped to take a closer look and felt that the wheel was loose. The quick release had been flipped open. The axle was still finger tight so the wheel wasn't dropping out. The lever was positioned against the front fork so except for the curve of the handle it looked normal.
I might have thought it was an accident or oversight on my part, except I transport my bike without removing the wheels and I had done a full bike check at the start of the ride. I hadn't checked the quick release itself, but I had checked the front wheel and it was tight and spinning normally. My suspicion is that someone messed with the QR while I was away and set it up so it wouldn't be noticed easily. I had ridden a couple of miles before is loosened up enough for me to notice. Luckily I didn't hit a pothole or something that would have popped my wheel out.
Never expected anything like this. Probably just a prank, but a dangerous one. For now on I'll be checking the wheels if I leave my bike for a while.