Sorry this is gross but I am concerned

I know for a fact I put a tampon in last night before I went to bed. I also know for a fact I didn't use the restroom at all last night yet this morning when I went to pee I didn't hear or feel the tampon plop into the toilet. Usually if one is in over night it will just fall out when im peeing (sorry for being graphic). So I went to feel for the string and nothing was there. I used the plunger and checked the toilet under the toilet paper I had thrown in there and didn't see anything. I am totally confused. It doesn't feel like I have anything in there either so idk what to think. I put a clean one in and im hoping there isnt some super old tampon just chillin inside of me right now. Has this happened to any of you and what did u do??