I had an implanon for 3 years which was successful and time came to have a new one inserted. After a month I couldn't feel it anymore and after 4 months it wasn't agreeing with me so I went to get it removed. After 2 ultrasounds and a MRI of my arm they said it is not there. They said it can't move out of your arm and it is a mystery. I don't understand how something can disappear. Should i be concerned?