IUD Expoltion?

I had the 3 year IUD inserted 7 months ago. The procedure went fine and I have had no complications but last night I felt some pretty good pressure near my cervix and when I went to check my IUD strings my IUD was actually in my vaginal canal and not in my uterus... I grabbed the strings and gently pulled; it came out with no real pain. I'm curious to know if this has happened to anyone else... ?