Another possibility, maybe she layed a 2nd clutch of eggs and is now setting again, as her others are older and doing well on their own.
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Well, I don't know that they are either, it is all purely speculation, the goose is missing and you were looking for reasons why? She could also have sickened and died, maybe she was old... All we can do in response to your post is speculate really.
Another possibility, maybe she layed a 2nd clutch of eggs and is now setting again, as her others are older and doing well on their own.