Was I mean?

I work in a school library and am in charge of getting overdue books back. Mostly they are from students, but every once in a while we have teachers who forget they have books checked out. Teacher books check out for 3 months at a time before showing overdue.

A couple weeks ago I sent email reminders to teachers with overdue books and let them know they could return them or to let me know and I would recheck them if they still needed them. Most books came back, but one teacher had over 80 overdue books. She emailed back and said that she’d get them back. I asked if she wanted me to recheck so she could keep them, and she said no, she’d bring them back.

A couple weeks had passed and she still hadn’t returned them, so I thought maybe a physical reminder she could hang up would help (i know teachers are busy), so I ran a report with titles of the books and put it in her mailbox with a note that said, “Just a reminder: you have overdue books. Please return them when you can. Thank you!”

She returned them after school yesterday. But this morning my boss said that the teacher had come to her in tears because she was so upset about the note I’d left. I feel truly awful, but at the same time I don’t see what was so wrong about it or why she is sooooo upset. Am I missing something? Was I mean or rude? I was just trying to do my job 😕