I thought I just saw someone with (what I believe to be) a thunderbolt 3 and a disc drive on their MacBook, and I thought there were no more disc drives that were built into MacBooks (that have thunderbolt 3 ports also). The computer did look like one of the thicker, somewhat older MacBooks. What did I possibly see?
Could it have been a Kensington Lock Slot? I believe the pre-retina MacBook Pros and MacBooks with optical drives all had them.
(Image: Wikipedia User "Yetzt", CC-BY-SA-2.0-Germany)