Trading yours for one with a safety is about the same as adding the safety, I believe, but I have a very customer friendly gun dealer.
First, I moved from Glocks to M&P's (ergonomics, mostly, although I got $300 in rebates, since I traded 6 for 6, not all at the same time)
Now, I am moving to add the 1911 type safety. You almost have to engage and lock it while using the slide release lever, as your thumb goes under the manual safety, not over it, unless your thumb is like Doctor J's. Slide closes, round is chambered, safety engaged.
Unfortunately, bad things can happen to passive safety design handguns, despite that we think we are taking all precautions, double checks, etc.
Fortunatley your friend avoided the femoral artery and femur, or he could have been in serious trouble ( doesn't take terribly long to bleed out from severing the femoral, and a busted femur is 6 months of surgeries and recovery time).