Yes you might be right, but I'm not seeing the connection big data could make between myself and my patient other than maybe our phones were in the same geographical location, but so were 50 other people on that day. How do you think your relative's phone knew YOU were doing the search? I don't doubt there is a connection somewhere and I'd be supremely curious to have a data scientist chime in.
May not have just been you. Lots of people may have started getting them. Also you said it’s an unusual diagnosis, some keywords are worth more than others, it may have triggered an aggressive ad campaign.
But for the record I think you’re right, I think there is more nefarious, invasive targeting going on than they admit. Also Bluetooth proximity, UWB, lots of ways to associate your two phones closely together, which is something Facebook at least has quietly admitted to in the past. I know Apple has protections against this, but I also know Facebook has an entire department of people dedicated to hacking the iPhone.