User buys item, want it to disappear from her feed

tldr. I’m trying to figure out how to make an item not visible for a user’s feed if the item was purchased.

A user sees a feed of items to donate to. A user can choose an item and buy/donate. After the purchase is complete I want the item to be removed/invisible on this person’s feed. Any ideas on how to do that?

Purchase makes an entry in “App: Sales” sheet. I believe this sheet will have username and SKU/item name of the purchase. Then build some sort of formula to exclude items user has bought.