Can your tampon get lost in your vagina?

No, you cannot lose your tampon inside your vagina.

Your vagina is only a few inches long, and a tampon can go no further than your vaginal canal because the cervix stops it from going any further than that. If you have a tampon in your vagina then it's not going to get lost, you know exactly where it is and can remove it. Someone forgetting a tampon does not mean it is possible to lose a tampon in the vagina.