If another one is gone in a few days, you may have a black snake in the coop/shed, or with an access hole to it. It doesn't have to be a very big hole for him/her to get in, I have seen a photo of a black snake that had eaten an egg, and then didn't fit out the hole it came in by - half in and then 'corked' half out. One way to find the hole, I guess.

I can't see a rat taking only one egg, though it might (try setting a rat trap where the hen can't get at it, to remove that possibility) and 'coons or 'possums would take the hen. The other possibility is that the hen accidentally broke it and ate it, but this seems unlikely.

Hmmm. I had rats last winter, but I thought that was taken care of and this fall when I saw some evidence of a return I dealt with it again. But maybe they are being persistent as the weather gets cooler.

I have never seen a snake on my property. That doesn't mean there isn't one, though.

Is it unusual for an egg to "disappear"? Oh, Lordy, I hope I didn't just sell it to the little old lady down the road!

--Johanna