While I do respect you and your spouse for trying this experiment, it's entirely too small a sample size to really prove that this doesn't happen. There are a ton of variables involved, the biggest being which advertisers may or may not be listening in at any given time. It's hardly a controlled experiment, and I can't say I can put any stock in it.
It also does not prove that it is observer bias. I have had things pop up that I am %100 absolutely positive I never in any way shape or form looked into, yet there the ads were after a short conversations with others who did have an interest.
It makes sense for them to target by IP, so if one person in an office is researching the product they can start targeting the entire office and maybe get their ad in front of an exec who can make a purchasing decision.
Also a fair number of people live where a snowmobile isn't practical but have a cabin where they are and so they will be making weekend trips to where they are practical.
Your point stands though, anyone who lives in the wrong area is unlikely to be targeted if the only indication they might want a snowmobile is home conversion. If you are serious you will do other searches (tracked for sure), and have location history in a target area (might not be track able, these area often have poor cell coverage)
at the end of the week, we both saw no increase or even a mention in our targeted adverts regarding snowmobiles. likely what is happening is that you searched something somewhere on your phone, then brought it up in conversation, then saw an increase in ads related to that subject.