Earlier quoted context omitted.
His phone would have to be running a hotspot for any visitors (in many parts of the rural area in my locale, mobile data is it for the internet) but if any visitors were with the same carrier network, visitors could have searched. However it's entirely improbable any of his buddies would be on their phone while they're there unless it was a legit interest. Secondly this is stuff from what I gathered, some of is stuff…
I’m basing my reasoning on the assumption that advertisers (such as google, meta, tictoc) are aware of your location at all times . (See: https://news.ycombinator.com/item?id=42909921 ) Based on this assumption, it wouldn’t be necessary for any of your friends to search for the topic during an evening together.. it would simply be enough that one of the friends showed some interest in the topic prior to the hangout (…
As such, if location or device id data were available to build a larger picture, for any sort of common topic I'd agree the advertising could easily be a result of data analysis of various subsets of phones in a given region, applying algorithms and feeding it back into search results.
However like I said, the stuff was apparently way way out there zany - he ensured me he would ever bother searching for it. So zany in fact no one would ever bother. For all I know he may have ruled out other people and have just been talking to his pet dog and various other tame native animals that hang around his verandah. I would tend to believe way way out there as after a small smoke around me he's dribbling worthless bs. There's no low bar on my part either - something like if polka dot dogs exist I could accept as something that might / could be searched the next day by anyone who was involved in such a out there conversation, and as a result skew search results.
Any how I'm settled on it's one of the many worthless apps on his phone that exists because a website is not desktop friendly - as they say if the service is free, you're the product ...