I don't think the BSFL ate your worms...at least not the live ones. However, if you had a very heavy infestation in a relatively small bin, they could have made the environment non-conducive to worm health. By that I mean BSFL do a great job eating stuff, but in the process they produce some funky waste that seems to be fairly high in ammonia. (I have not tested this but am judging by the funky smell.) This in turn may have started killing off your worms, which then became a high protein snack for the larvae to consume.

I would bet that you still have alot of cocoons in the bin to salvage your colony and maybe a fair number of worms down deep in the compost.

Your worms might be hiding at the bottom esp. because you mentioned: ""It was a touch drier than usual ""
How hot has it been?

It's been 110 degrees all week until today. It cooled off to 99. Wohoo!
Glad to hear they might be hiding or at least I may have enough cocoons to recover them. This is certainly the hottest it's been since I got them. I had the BSFL last fall and all seemed fine but I have a lot more worms now. It was pretty dry except the very corners, hopefully that's all it is.