Ask HN: Amazon tracks information of what you buy outside

So this happened today. I bought a trouser this afternoon from high street (paid cash since it was a round figure) and then bought a meal in KFC which is also in high street just few metres away (this time I paid from card). And importantly, I don't carry a smart phone (so no amazon app, wifi triangulation, etc). When I open amazon at home - suggested items are trousers!! I haven't made any search in amazon relating to trouser or men's wear. How can Amazon make suggestions without tracking my payment on high street. Im guessing KFC payment data reached Amazon from which it has inferred I was in high street and so on or it can be cellular tower data ? ) Has anybody else noticed similar behaviour. edit: minor correction to sentence.