leaving a tampon in for a week can be dangerous im pretty sure, and im sure eating it isnt exactly good for you either but leaving a tampon in for a week is pretty much a guarantee something bad is gonna happen
I know that it's not safe to leave a tampon in for an extended time in a vagina.
That's how you can suffer from Toxic Shock Syndrome.
I'm not sure of how the star fish reacts to such things however. It's still an absorbent part of the body though, so I suppose it's probably not ideal to leave something so unhygienic in it.
Also, you will have to remove the tampon at least a few times in that week, and then reinsert it, at any rate, because you have to poo. That's only going to make it an even worse hazard as the week goes on.
Perhaps it is better to eat it. Hopefully your stomach acid would fight off most of anything harmful on it, and then you'd pass it within a day or two.