Depends where you are located. I'm in SoCal, so it could have been a coyote, hawk, big cat or dog, raccoon, etc.

Southwest KS, my entire yard is fenced, shadow fence, 6 ft. I don't believe a coyote or big dog could make it. whatever it was, it came at night.

Around here, turkey vultures do a lot of cleaning up of animal carcasses. They do only dead stuff, and they work fast. They aren't nocturnal, but an owl probably wouldn't hesitate to take it, and they are.

could have been a possum too.

Cat, fox, coyote, bobcat, or any bird of prey could carry it away.

And your 6-foot fence won’t stop a coyote any more than it will a cat.

We've a six foot fence and I've seen a coyote jump it.

ETA: Some domestic cats will carry off all sorts of dead stuff.

ETA: Doves will fake being wounded to distract from their nest location. Will they fake being dead?

Well, whatever it was, it didn't even leave a feather behind.

I think it was probably a raccoon. I had a coon kill 2 of my chickens in a very secure run (well, I guess not secure enough). I buried them fairly deep and put fencing over it. In the morning, the bodies were gone......not a feather left behind. I think coons carry off their kill sometimes and eat it elsewhere.

Solved the problem of the missing corpse. Today I found a pile of feathers when I started to cut down peonies. don't know who hid it there tho.

I had a large squirrel disappear by morning after I hit it with my car. Nature has ways.