Silicone doesn't have to be in the blood to cause us these issues, I believe. For one thing, I think it can take time for the body to realize the silicone IUD is not there. If indeed we are in a state of autoimmunity from the IUD, then it can take time for the body to rebalance and correct that. And the hormonal imbalance caused by the IUD can mess up other systems in our physiology. It takes time for the body to correct this too. My Dr. says "entire kingdoms rise and fall under the influence of women's hormones." He just needs to realize that the Mirena can cause such an imbalance!
My research on adrenal health-related autoimmunity, dysregulation of the autonomic system, and the HPA axis has shown me how imbalances can affect so many seemingly unrelated body systems and therefore cause the symptoms we have.
According to many sources I've seen, silicone can be hard to remove. Some say it is impossible. I don't know. Maybe you can be glad that there is no silicone showing up! It just means you need to look at what it takes to rebalance a messed up body: time, good nutrition, stress management, etc. This is just my theory and personal feelings, and I hope it proves true for me as well :)