I just read an article on Substernal Thyroid and I don't have any of those symptoms. The doctor's believe it's my cervical spine. I'm going to give my post operative notes to my GP to read and tell me where the right lobe went. The surgeon that did the surgery up and left for TX. I appreciate your repsonse though. It really helped.
Thyroids can die off. In diseases like Hashi's where antibodies attack the thyroid over time, the thyroid often eventually "dies". Once it is no longer functional, it can atrophy (shrink), but I think that a total disappearance in just 9 years would be pretty rare. Perhaps you should check back with your surgeon and try to reconcile what's going on???
Did you find a cause for the swelling? Just a thought, but you might do some research on substernal thyroid.