Nobody else had a phone with them. There where only the two devices I mentioned above. Both connected to the same WiFi network.

That’s a good question. Boredom led to the convo, I wasn’t using my phone at the time but even if I was “googling”, I would’ve been using duck duck go.

Did you buy those cereals recently? What method of payment did you use?

I didn’t, a family member did buy one of the two via credit card. Could that be it? The. We got associated via the WiFi network?

Very possible. Facebook and other social networks (and their SDKs embedded in every mainstream app) use IP addresses as a way to infer relationships between people.

Data aggregators can/do get the purchase history of people and will associate that with their marketing id, I built systems to do this and it is amazing how detailed it is. This includes in store purchases, digital purchases, and can even include cash purchases if you have a store discount card etc.

Generally IME we would get other devices associated to that user. e.g. If Sam bought something on his cell phone, when we aggregated that data or purchased it from others, we could associate Sam's other devices (computer, tablet etc). Typically we would only target this consumer based upon their marketing id across devices, and not target associated devices which didn't match to the user. However, there are some aggregators that do track devices commonly seen with the user, regardless of a known marketing id.

So not impossible you could have been targeted this way.