Went in for followup u/s for left thyroid nodule. came back as nothing on left but new nodule on right. worried they got the sides mixed up. possible?

Not likely: Ultrasound exams are performed by trained technicians and supervised by physicians on site, so a mix up is unlikely. It is, however, common for many people to have multinodular goiter, meaning many cysts on both sides of the gland. These are usually benign & require no further evaluation. If concerned, a needle biopsy can be performed.