This happened to me today with my sr9c. Must have brushed the gun up against the bed of the work truck and switched the safety on. This also was the first time thats happened, I've brushed safeties on and off (1911) quite a few times, so much so that I check them quite frequently throughout the day.
O and my vote went to the xds for the lack of the thumb safety. Both good guns but my preference is the springer since I've never failed to disengage the grip safety.
Case and point. You can not just disregard a thumb safety and leave it off. Well...you can, but it's a stupid thing to do.
and I agree with your point on the xds. I've even tried loosening my grip as much as possible (withing reason of my grip...obviously I can grip it in some completely stupid way and not engage it) to see where the safety will cause the gun to not fire, and I do not get any malfunctions. It is a well designed passive safety.