I have my sales "hidden" mind you so how is it possible that I am getting favorites for an item that sold out two days ago?
it happens all the time. Your sold out item was probably in somebody's favourite list
maybe it was in their favourites. maybe from someone else's favourites. maybe from an internet search. lots of possibilities.
If you are sharing links on social media - instagram, pinterest, facebook (or someone else is sharing these links), then someone clicking on it will still be able to view the listing and favorite it. If it's an item that you relist regularly, it should also appear in your feedback if previous buyers left a review.
Possibly a customer had viewed it before and it popped up in their recently viewed feed, they had it in their cart and saw that it was sold so favorited it, it was in someone else's favorites that they looked at and they favorited it. I'm sure there are more ways, but yes, it is possible.