[mi100hael]

In this case, the ad network would presumably not know or else they wouldn't keep showing you ads.

But it's worth noting that ad networks are more interconnected than most people realize. You can go to Facebook and see the "off-Facebook activity" they have received about you from partners, many of which are retailers. I imagine purchase-history is part of what's shared if you make purchases with those retailers using a email/phone number that's also associated with your Facebook account.

https://www.facebook.com/off_facebook_activity