My take is that uke doesn't want to tell him he lost the keyring (or whatever that was) because it was a gift and he wants to treasure it but admitting he lost it would hurt seme kun. But tbh I think it would be better to just be straightforward and admit it cause all humans make mistakes ╮( ̄▽ ̄)╭
why lie... Why just why... Like I'm so confused, just tell him the truth.