Ask HN: How Are Brick and Mortar Stores Retargeting Online?

I thought this was just a coincidence the first time it happened, but I've had enough "coincidences" in a row now to see that it's deliberate. I've been buying things at physical locations (i.e. grocery store, walgreens, etc.) and then seeing an add for that exact thing on Instagram in my feed. The same thing happens to my fiancé and, tbh, it's kind of pushing the realm of privacy in my book. I understand that if I buy something online or on my iPhone, I'll most likely be retargeted somewhere else online. But, this is a physical store, where I physically pick something up and hand it to a person and bear through small talk while they ring me up. The only connection I can make is the email address linked to my credit card is the same one on my Instagram account - but that would also mean Instagram (Facebook) is providing access at a low enough level to allow the ad network to know my email address. Is anyone else experiencing this?