* the "somehow we talked about a college" is because someone else at coffee was looking at something college related and it was recently on their mind so they brought it up. You're associated with those people, so ad agency it decides to show you an ad. It may do this a lot, but the times it actually works really stick out to you.

* After the coffee, one or more people search or perform actions associated with that college. Ad agency knows you were recently meeting with them so decides to show you some associated ad.

Keep in mind that the ad agencies, whether Facebook or Google or some lesser known but still large one, have their own profiles of you and who you associate with.

I think Occam's razor holds that since we know there are multiple agencies tracking what you do and who you do it with online and that can conceivably be used to explain most of this, it's a much more likely explanation than a large company outright lying in a way that would have a horrendous backlash if proven (and it's not really that hard to prove if people got serious).

Edit: whoops, not that hard to prove...