You purchasing the product should have fired a "conversion pixel" which would now exclude you from being a valid user for seeing the product ad(s) in question.

You purchasing the product should have fired a "conversion pixel" which would now exclude you from being a valid user for seeing the product ad(s) in question. The advertiser is just wasting money if they're not using a conversion pixel. (Unless you meant just clicking "I bought it" to get rid of retargeting ads in general, not that you actually bought the product)