A finch egg was stolen?!?!?

So the finch in my backyard had an egg in her nest. The next day she had another one and now has two. Now (third day) she only has one? What happened to the egg? If a predator came don't you think it would have taken both and knocked the nest down in the process? The mom came back a few hours later after i saw that there was only one again... and is now sitting on her one egg...