People that really panic probably have a lot of difficulty getting back into the water, so its probably going to be rare to find them active on scubaboard.
I was diving off Palm Beach Florida with a group consisting of all locals who dove several times a month or more (most a couple of dives a week).
We were doing some deepish reefs (110') and mild decompression profiles (mandatory 10 minute stuff). It was group drift diving without 1-on-1 buddy assignment, which was the norm in that area at that time (may still be). Anyway, I turned around and looked into the saucer eyes of another dive flailing around and pointing at her regulator. It was evident she was having a crisis, but the reason was not clear. We'd been down a while and had a ceiling by that point in the dive.
Since I dove an air2 at the time, I popped my primary out, she grabbed it, and I held her tight by the BC straps making sure she didn't rush for the surface. After a minute of hyperventilating she began to calm down. She reciprocated a nice hold on my BC straps and we started for our decompression stop. The entire group (maybe 7 others) joined us in the ascent as the activity at depth was noticed by all.
Anyway, time past, the ceiling was lifted, and we surfaced and returned to the boat. I had a whopping 300 lbs - my remaining air had been actively monitored by the others at the stop in case we were forced to modify the buddy breathing configuration.
On the boat no abnormalities could be found with her gear at all, although I have no idea if anything was discovered in the shop.
She claimed I saved her life and also took my name and address. About a week later I got card from her thanking me, and once again crediting me with saving her.
To your point, she was never seen diving again. To this day I have no idea what she really experienced or why. She was surrounded by divers the whole time and seemingly always within close reach of air. My saving her life was really just winning the proximity lottery. It did make me wonder how achievable a 110' flared emergency ascent would be - of course followed by ordering up some O2 and an expensive trip to the chamber.
Final note, back in the early 90's mild deco profiles were pretty normal off Palm Beach and nitrox was just becoming available. Haven't dove there (or put a ceiling over my head) in many years.