I had this happen many years ago, to the point there was no chance something wasn't listening. We suspected it was my partners iPhone with Facebook installed before they got better about preventing abuse like that, as it was a Facebook ad that showed up.

Were talking about something where we never use the product, would never use the product, but it came up in a conversation just between the 2 of us, and there were ads the next day.

It happened a few times.