Something similar happened to me. I blacked out for the first time with a tampon in. I woke up the next afternoon with it have been in over 24 hours and I freaked out. I had some symptoms and made my dude friend take me to the ER. Turns out I was just dehydrated. I'm a worry wart though and always expect the worse so it wasn't really out of character for me to freak out and go.