Tampons cannot go into your body, get lost, and float around. So if you did put in two, you would be able to pull two out. Your v****a is like a tube with two ends. One end is where you put the tampons in. At the other end, there is something called your cervix. Your cervix opens up during childbirth, but otherwise stays closed so that nothing can go into your body far. So you could get into the shower and feel around for a tampon. If there is that extra one in there, it can't be too far up, so you should be able to at least feel the string.
TSS is serious and rare. A variety of nasty symptoms appear can quickly appear.
"Toxic shock syndrome from staphylococcus starts suddenly with vomiting, high fever (temperature at least 102 degrees Fahrenheit [38.8 degrees Celsius]), a rapid drop in blood pressure (with lightheadedness or fainting), watery diarrhea, headache, sore throat, and muscle aches. Within 24 hours, a sunburn-like rash appears. There also may be bloodshot eyes and an unusual redness under the eyelids or inside the mouth (and v****a in females). After that, broken blood vessels may appear on the skin. Other symptoms may include: confusion or other mental changes; decreased urination; fatigue and weakness; thirst; weak and rapid pulse; pale, cool, moist skin; and rapid breathing"
http://kidshealth.org/parent/infections/bacterial_viral/toxic_shock.htmlIf you notice these symptoms, you will need to go to the doctor. So far, you just have one symptom, so it certainly could be a coincidence, but be on the lookout for the other symptoms just in case.