It could be the ads came up a more conventional way - the makers are priming the publicity for the game so it shows up in magazines and ad buys etc. If you and your friends are avid gamers - you probably get some early exposure before more general ad channels buys show up.

But to really answer this question, we could build a better experiment. Write out a set of topics on index cards. You have to be careful that topics aren't new product rollouts (otherwise you really have to think about how you decided to write that topic down in the first place). Draw a card, don't talk about or search the topic for some amount of time, then inject the topic where it might be observed (talk about it and/or search for it somewhere), then for some amount of time, see if it comes up.