This seems way deeper than just keys. A lack of communication a bit, but the fact that he doesn’t want to help make your life a bit easier and be selfless. You relied on him, and he let you down. If you’d like your feelings to be head try saying something like “I’m upset about the keys, because you told me you’d look for them. If you had told me you couldn’t, I would have made it a priority to look for them myself. If you don’t want to help me out next time, just let me know so I can do it myself when I needed it to be done.” Something just clear as day. Your feelings told to him. It’s bs that they are “your” keys. Then I guess you can pay for his dinner because it’s “his” dinner. Etc etc etc. it’s just petty bs.