Skyla IUD

Hi there I'm currently stressing because I had the skyla IUD inserted last year in august and ever since then I've had regular periods on time for about the same length. This month however, I haven't gotten it and am 6 days late. I tried feeling for my IUD strings several times with no luck. I've done it plenty of times and have always been able to find them. It no luck whatsoever. Has this happened to anyone?? If so please give your best advice and/or opinion.. thanks!!