Similar thing has happened to me before. One of the girls I punted came up as a friend suggestion on Facebook. I had saved her number on my normal phone and I’m guessing some how Facebook had access to my contact lists and then made the suggestion. I just ignored it. That’s just creepy!
Anyhow, since then I’m off social media completely, the only one I use is YouTube, and that’s not even a proper social platform so to speak.