AD and Thumb Safety
Interesting question, which I cannot answer, since I was not allowed to examine the pistol I mentioned. SInce I had offered it to my friend, he immediately paid up and it disappeared.
However, when I was about fifty years younger than I am today, I obtained a DWM 1918 pistol, which happened to be the only handgun I didn't have to sell to pay the rent and buy groceries. It was kept loaded and locked, with Winchester hardball in the magazine and chamber.
At about 3AM one morning there was a loud pop from the direction of the hall in the apartment house where I was living. After several of us searched without result, I retired to my kitchenette for a cup of tea and had a horrible thought. Oops! Guess what? The pistol was in the pocket of a leather WW-I aviation jacket hanging in my closet.
On taking the Luger apart, I noticed that the firing pin's sear notch had sheared off and the stub looked grainy. The fired case was still in the chamber and the safety lever was still in the up position. I did not note any damage to the safety bar. This was probably due tot he fact that the Luger is a true locked breech action that was actually a reduced version of the Maxim machine gun action. The pistol does not begin to unlock until the pressure in the chamber has dropped to zero. Although the safety bar stopped rearward unlocking motion, the heavy 40 pound recoil spring had absorbed enough momentum to prevent damage.
The 1911, being not a locked breech design, but a delayed blowback (there is still pressure against the case head when the pistol begins to unlock and part of the rearward motion is blowback) there would be collateral damage to some working parts, such as the thumb safety if the pistol fired loaded and locked. As I said, I have never heard of this happening...it was certainly not in any of our ordnance manuals, and they covered every possible serious malfunction and accident known at the time of publication.