Is Facebook rummaging through my phone?

• I had a couple of very odd experiences with the Facebook mobile browser page (Chrome for iOS on an iPhone 6) that seem beyond coincidence, and it makes me wonder if Facebook is rummaging through my phone, or if iOS is giving some kind of privileged access to some of my information to Facebook. To provide some background, I am a very rudimentary Facebook user. I have approximately 10 friends who are all immediate or extended family and one contact from my church. I have no contacts who are professional acquaintances, nor would any of my existing friends know any of my professional contacts. This account is about a year old. I previously had an FB account with a little over 100 friends, but was beginning to tire of Facebook, and had my account deleted (or so I understood) about 3 years ago. I have only come back to satisfy my wife who finds it a convenient way to share stuff with me that she finds interesting. My only access to Facebook is through their web interface, on a PC, an iPad or on my iPhone. I have no native Facebook apps installed on any device. With all that said, twice this week I have had the experience of receiving a phone call on my iPhone from someone I work with, once from a fellow employee, and once from a client contact, that was followed very shortly by the appearance of that person in the "you might know" list that Facebook presents to prompt you to grow your friends list. The first time this happened, on Tuesday, I thought "how weird, I can't think of a single association with my existing friends that would prompt Facebook to show me that person". The second time happened this evening, and freaked me out even more. The only actual association that I can make between these two events (or four? two calls and two you-might-knows?) is that I received their calls on the same cell phone on which I later viewed the you-might-know notification. Neither of these people are particularly common contacts for me. The first I've only known for a week, and the other several months. The email address that I registered to FB with is not my work address, and neither of the people in question have any reason to possess my email address. I have not registered my phone with Facebook either. I can see no reason at all for either of these coincidental occurrences, much less both of them, so close together. Given my understanding of current browser behavior, I am no longer surprised if I click on something at Amazon or some other e-commerce site, and then later see that item show up in an advertisement on a news or sports site. I understand that there is metering and observation going on all that time and that some super-cookie can broadcast my preferences to anyone willing to pay the price, but to see this behavior crossing out of the browser and between distinct applications on my phone, including my phone, is deeply disturbing to me. Am I just imagining this or is my phone somehow giving up information to my browser that is unrelated to my browsing activity?

• Answer:

  If their mobile Facebook app is set to synchronize with their phone contacts, and if they added your phone number to your contact details, then Facebook now knows your number (but won't show it), even if you didn't volunteer it. Then when they call you, Facebook knows it, and will attempt to leverage it.