Same here. I was visiting a friend who just moved in to her new digs and the landlady has an Earth Machine in the backyard. It was anaerobic because she is a vegetarian and has lots of fruit and veggie waste and trimmings, and I didn't see a shred of newspaper or any paper product or dry leaves. The inside of that composter is a slimy, stinky yuck. The worms seem to thrive, lots and lots of them and FAT. So there is pure 100% worm food (including onions, cabage) and worms only. All that food and moisture didn't kill the worms.
And here I am, caring and tending to my worms in the bins, make sure the bins don't get anaerobic and they are only half that fat.

I recently made the same discovery in my compost bin. I've harvested over 2 lbs. of red wigglers. They are now happily squirming away in their own flow through bin. I'll leave the worms remaining in the regular compost bin alone for 2-3 months before harvesting again.

I used to see the same thing when I had an outdoor compost heap. Feed them and they will come.

On a similar note, my grandparents lived on a ranch next to a river. My grandmother made "mush" (= hot cereal) for breakfast *every* morning. If there was any mush left over, she would bury it under a stone next to the veg garden. Whenever we wanted to go fishing, we would dig under that stone to find the fattest worms to use for bait.