I had my MIUD inserted 3/07, 6 weeks after having my second child. When I went back to my doctor for my 4 wk check-up, my doctor couldn't find my strings either. After multiple unsuccessful ultrasounds to locate the IUD at the office and hospital, my doctor suggested removal with D&C and Hysteroscopy. After the procedure I was heart broken to find that they still could not find my Mirena IUD. Recovery from the procedure was relatively easy, but since it was totally unnecessary in my case, I was very angry. Finally my doctor ordered a CT scan and discovered that my IUD had perforated my uterus and was embedded in my upper bowel. I fortunately had no pain from it, but was freaked out. I eventually had the IUD removed via laparoscopic surgery and had my tubes tied at the same time. I would make sure your doctor knows exactly where the IUD is before letting them do any surgery. I wish you all the best.