Perhaps a remnant, an ectopic piece of tissue, anything.... reasonably confident that complete and total absence of a thyroid is incompatible with life, especially in settings of an acute stress (infection, hypothermia, trauma, drug, etc, etc), 2o/2 myxedma coma. Check a thyroid panel to convince yourself this is so. While the TSH may be sky high, I doubt the T3/T4 will be dead zero.
Is the patient s/p ablation? Surgical removal? Congenital absence?
Does the patient have physical signs and symptoms of hypothyroidism?