Worried! Lash egg in nesting box but everyone seems fine?

[Nicky S]

I was just cleaning out the run and coop and found a lash egg in the nesting box. All my girls are acting normally, however. I did have one girl come into the house last week as if she were testing out a new laying spot briefly once or twice, but that's the only thing I've noticed, and they are all eating and moving around as normal, and frankly look very healthy. Nobody is laying right now - they all had hard molts this fall and stopped, and then it was short, dark days so they haven't started up again. Everyone is 3-4 years old.

Could this be a one-off? What should I do if I don't know who it was? The vet is also closed today as it's Sunday. Trying not to panic.