After waiting almost two and a half weeks, I found it yesterday. I think it was the head chicken Madea that laid it. She's an Ameraucana, the oldest, and has been walking around for days with a piece of grass in her beak arranging it in different places like she wanted to build a nest. But she actually laid the egg in the nesting box, not under the coop in the dirt hole, which is great! I had a round yellow rose-scented candle in there, cuz it was the best egg-like thing I could find in my house. Lol.