There was someone I was meeting in real life but we had absolutely no FB connections. No mutual friends. And I didn't even know she was on Facebook.
Suddenly I saw her on my 'Suggested friends' list.
The only reasonable explanation is that she found me on Facebook and viewed my profile. Facebook saved the incident and suggested her to me as a friend.
Facebook forgets nothing. Nothing.
Export your Facebook data and check out they keep your message history with everyone forever.
Unfortunately they do not have chat logs from before 2011, when chat and messages were merged.
https://www.facebook.com/help/405183566203254
So if you delete it, it won't be in the download.
Several times I've been at a particular venue, without "checking in" or even posting. The next day, people I met at the venue would show up in my suggestions list.
Using rooted android you can make a seperate permission dialog pop up every time an app tries to access certain APIs.
Despite having all GPS related features of Facebook and its messenger disabled, the Facebook Messenger app tries to access my GPS location at seemingly random times.
This is troubling, and goes against the Play Store's terms and conditions for app developers. I suppose Facebook gets a pass on it through some unspoken agreement with Google, though.
This. I had something similar happen a year or two ago; I enrolled in a course at a local university, and about midway through the semester Facebook suggested that I friend the instructor.
I was friends with no one else in the course, had never posted about the course on FB, or anything else that I could think of.
Of particular note was that his had all happened after I had to drop from the course due to health issues.
Then I guess WhatsApp picked up that change and sent the data back to the Facebook servers. An hour later, the person showed up under Suggested Friends.
When you look someone up, there's a significant chance that you will appear in their "suggested friends".