Learn Turkish: Yüzüğü kaybetmiş mi? - Did she reportedly lose the ring?

kaybetmiş uses the inferential or reported past tense (-miş). You would use kaybetti mi if you were asking about direct facts. You use kaybetmiş mi when asking about something you heard from someone else, like gathering gossip or asking about a rumor (Did you hear if she lost it?).

I know the word for 'lost' is kayıp. How does it become kaybetmiş?

kaybetmek (to lose) is a compound verb made from kayıp (lost) and etmek (to do/make). When they join, the second vowel of kayıp drops out, and the p softens to a b. So, kayıp + etmek becomes kaybetmek, and adding the reported past suffix gives us kaybetmiş.

Why does the word for ring (yüzük) change to yüzüğü?

Because 'the ring' is a specific, definite object being lost, it takes the accusative case suffix -ü. When you add a vowel suffix to a word ending in k, the k usually softens to a 'soft g' (ğ). So, yüzük + -ü becomes yüzüğü.

How do we know the sentence means 'Did she lose' if there is no pronoun like 'o'?