Soldato
Id be surprised it it was actually INSIDE the the weetabix from the start.
Why?
That'd be the obvious place for it to be, it'll have fallen into the mix, then squished inside when it was formed into bricks.
Don't know about you but when i'm making breakfast in the morning I don't tend to inspect my cereal before chucking it in a bowl and slapping on some milk. Not to mention I'm usually half asleep, making a brew, and thinking about what stuff I need to take with me today.
Quite easy to miss something you don't expect to be in there.
I've had it before where I've had a big chunk of cardboard inside of a sandwich.