I am surprised that they did not remove the entire thyroid to make sure the cancer was gone....my tumour appeared to be encapsulated as well however microscopic analysis of the nodule once removed showed that there was "vascular invasion". As a result, we decided not to take any chances and my surgeon did a second surgery to remove the remaining half of my thyroid. (The only reason he didn't remove the whole thing during the first surgery was that the nodule visually appeared to be benign. We had already agreed that the entire thyroid would go if it was cancer.) I think the sonogram is a good idea, perhaps followed by a radioactive iodine scan to fully see whether you have any more nodules and if they are "hot" or "cold". The good news, from what I understand, is that recurrent thyroid cancer is almost always successfully treated if it's caught early by removing the nodule(s) and what's left of the gland and having a radioactive iodine ablation.
I really dont have any answers for you, but you have our support and encouragement. I am sure you are well aware that thyroid cancer is rare, only about 5% of thyroid problems are cancer. Try to stay calm and get all your tests done. I know this is easier said then done, but I am constantly clearing my throat from the hypo symptoms, so maybe thats all yours is. I have spoken to a few people who have had thyroid cancer and it seems reoccurance is even rarer then the cancer it self