Wow, awesome work guys! I'm always happy to hear that a potentially hazardous scenario was resolved with good know-how and team work.
I know of a specific incident where that exact scenario occured and resulted in a death. A guide was toproping with some clients and he tied an 8 on a bite and linked himself to it with a screw gate. The locker flipped and then rubbed itself open against the guy's stomach. One of the clients lowered him and he fell to the ground.
I used to use that exact setup, eight on a bite linked with a screwgate, until I heard about that case. And then I reasoned, well, I'll just use two lockers and oppose them. But seriously, at that point you're just making yourself heavier with those two lockers. My ultimate solution is just to stop taking the shortcut and tie in with the follow through figure eight every time. What ever that technique lacks in speed, it makes up for it in fumble proofedness and checkability.
Oh yeah, on the subject of tying knots in the life line. Dave, Dan, and myself all witnessed a belayer let the end of the rope zip through his belay device on Saturday afternoon. The climber was lowering and as soon as the rope passed through the ATC he started lowering a lot quicker.
Thankfully he was "only" about 10 or 15 feet up. The belayer felt like poop but the climber was relatively unscathed. This type of incident seems to be so freakin' common. Let's all step up our game and start tying those knots in the end of the rope.