Coins are swallowed every day.
When swallowed and they go in the stomach they pass uneventfully. If concerned, see your pediatrician. Sometimes after a few days and you haven't seen it pass an x-ray can show you where it is. I have not heard of any child dying from swallowing a coin in the GI tract. If it is in the windpipe there is choking
etc and that is an emergency.