Yes, more times than I can count! Several years ago at the Greater Pittsburgh Rod & Gun Club I was down in the pistol defilades well beneath the crest of the hill behind which the trap range is located. While standing in line waiting for my turn at the pepper poppers, I was struck - hard - in the back of the head by descending shot charges.
After the third time I got hit, I suddenly noticed that nobody was standing next to me! Everybody thought it was quite funny that I'd been hit 3 times in the back of the head within, about, an hour's time. They were joking with me; but, they were serious, too. The jinx finally got broken when another pistol shooter suddenly grabbed his shoulder and went, 'ouch'!
I guess what I'm saying is that when it's your turn, it's your turn; and, you're going to take the hit!
Years ago we used to shoot at an uphill pistol pit with a 100 yard rifle range behind a low dirt berm over the left shoulder. Once you were in the pit you couldn't quite see the rifle range; but, if that range was active, you would constantly hear the whiz and whine of centerfire bullet jackets and fragments flying just over the top of your head AFTER they had smacked into the backstop.
One thing I have against standing on the line at an indoor range is the metal target frames that other shooters on one or both sides will set at, about, 7 yards and start blasting away at. As pistol marksmen these guys universally stink; their bullet patterns are all over the target; and, you're absolutely correct, if they hit the frame you could get a piece of - not the bullet, but - the jacket coming right back at you.
The indoor range I use keeps everyone in the center of the room and close together - except for the guys they know can shoot. This protects their walls from being hit and allows some of us to be farther away from the shootout and flying brass in the center of the line.
I always wear expensive industrial grade safety glasses with photogray lens and large side shields; and, I've never regretted paying the price. Fortunately, what happened to you is rare; it does happen, but not often.
Still, things tend to run in threes; so, try not to stand close to other shooters for awhile. The good part is that when something like this happens the bounce-back angles are usually shallow; consequently, the farther you are to either side the better!