It does seem awfully creepy, but I guess if you care about privacy you're not using Facebook much anyway…
That night Facebook was suggesting I add my elderly neighbors as friends. We have 0 friends in common and I don't have Facebook installed on my phone (I just use the browser) so the only excuse I have is when they added me they must have some "share my contacts with Facebook" feature enabled. Now there's some forever connection between them and me on Facebook's servers even though I don't publicly link my phone number to Facebook, it's only added as a password/security recovery.
Everything about Facebook is, I deleted my account 4 years ago. Opened another one with a different email address last week. It instantly started suggesting people who I knew despite me not entering anything other than an email and phone number.
It's super creepy how it pretty much already knows who you are from data your friends have shared with it.
Maybe this person stalked me and that is why she appeared on my suggested friends page?
I think that's it. In quite a few of these 'creepy connections' I think it's usually something similar. If other people are anything like me, the first thing they'll do - when convenient - is to look you up on facebook.
That doesn't make it less creepy of course, but it can explain many, if not most of these situations.
Correct, but if the other person adds you to THEIR contact list, and shares THEIR contact list with Facebook, FB can then learn your phone number (without your Whatsapp ever sending it to FB).