Honey, your not the first nor the last to use the terms Tiny or Teacup.
If your not educated in the breed how would you know? That's what
YT is for. They will set you straight evertime.

I talk to people often when they see me with Buddy and they don 't
belive he's a Yorkie due to his size. When I tell them Yorkies come
in all sizes they still don't believe me. People think Yorkie and immediately
it has to be tiny or a Teacup, that's all they know & don't want to know anything else! I have learned to keep quiet, except on YT
Don't fret, nothing to be upset about. It's an honest mistake.
Your right, vet's don't know either