Send a card or note in the mail. Address it to her, at the school's address. I bet she would love a nice thank you note or card.

Put your return address and e-mail. Let her decide if she wants to write back.

More likely to be on LinkedIn I would think

Check LinkedIn

Type their name in the search bar. Or look through friends' friend lists thaat might have your teacher, the search their name in that section

You need pills?

Facebook or Linkedin would be your best option

Some people go out of their way to ensure they have no online connections. They do not all want to be found.
Call the school and ask them to ask her to contact you instead.

You could write a letter, (in cursive) to the school. Ask for the teacher's recommendation and include a SASE for a reply.

You ever use an actual fountain pen? They're spectact! Words just flow on the parchment!

Maybe she doesn’t have an account