Whose Shopping Cart?

I was at a large supermarket, and left our shopping cart waiting for me while I’d get something from a nearby shelf. My partner was shopping with me and he also went to fetch something. I approached our cart with the item I had fetched. At the same time, my partner walked towards another cart. Although I saw my shopping bag in our cart, for a short while I thought I had taken somebody else’s cart. Instead, my partner was going to take a wrong one, which caused me to suspect my own perception.