Ask HN: FB saving where you have been and using this to send notifications?

Yesterday, I decided to briefly pop by a coffeeshop after work, and bumped into an old friend of my brother, who I also have on Facebook. I didn't check in. I didn't even touch my phone while I was inside.<p>So far, everything is normal. I go home, and all of a sudden I get a notification. Your friend, X, has checked into coffeeshop Y. I wasn't tagged in the checkin. I never get notifications when friends check into places?! Has anyone here experienced the same thing? it felt a bit freaky if you ask me.