The best way that I know of is to get up in there and do some recon. If you’re unable to find the missing tampon and are still concerned, it’s time to call your health provider to have a look-see (don’t feel embarrassed! They address these types of issues all of the time). And don’t forget to see what our health expert Molly has to say on this topic. I’m sure she’ll have some great advice.
You should be able to find a forgotten tampon by reaching inside and feeling around. If you are uncomfortable doing this you should see your healthcare professional. A tampon left inside for longer than the recommended four to eight hours can be a risk of infection so be sure and read what Dr. Molly has to say.
The only way to know for sure is to put your fingers inside your vagina and see if you can feel the string or the tampon itself. Don’t worry, the tampon can’t go anywhere besides your vagina, so if you put your fingers in pretty far you’ll be able to tell if it is there or not. If you’re nervous or squeamish about it, try sitting on the floor on a towel with your legs spread wide and your knees bent (frog leg position). Gently open your inner labial lips, relax your muscles down there, take a deep breath and as you exhale, slip one or two fingers inside your vagina. Move the finger(s) around to feel the area and be sure to put your finger(s) all the way in. If you feel the tampon or string in there, just gently pull it out. If you don’t feel it, you can assume it isn’t there and insert a new one if you need to.
This is not intended to be medical advice. Everybody is different so please make sure to consult your physician if you're having issues. Do not delay or refrain from seeking professional medical advice from your physician because of something you have read on this site.