Roadside Repairs -- Cassettes

OK, I'm one of those irritating cyclists that asks you, "resting or broken" when I go past and you're on the side of the road. If your bike is broken, I'll try to get you back up and running. I've patched tires, fixed brakes, hardset derailleurs when the cable borke, but this weekend, I was stumped.

We pulled over for a couple and the problem was that the lock ring on the bike's cassette had come off (shudder...oh, the neglect that bike had seen). So, we explained about the lock ring, took the wheel off, cleaned the cogs that fell off, and proceeded to try to at least finger-tighten the lock ring.

Turns out during the time the lock ring was coming undone (or before for all we know), the threads had started to strip. We struggled to get the lock ring threaded. After about 5 minutes, DH, who is much more patient than I, managed to get the ring threaded. We tightened it as best we could by pushing the lock ring around with the screwdriver attachment to the multi-tool and then gave directions to the bike shop a couple of miles down the road. The ride sweep said they made it.

Another bike rescued, but....we almost failed to get the lock ring threaded. So, my question is...if we couldn't have gotten that lock ring on, is there a road-side fix that we could have used to single speed the bike? Or would this have been a fatal failure?