This is the 3378th most frequent Turkish word.
kaybetmesine
"Kaybetmesine" means "his/her/its losing" or "to lose" in a specific context (third person singular, dative case).
"Kaybetmesine" indicates the act of losing in relation to an object or goal, here being 'the match' and is used to show the emotional response to this loss.
Bu maçı kaybetmesine çok üzüldüm.
I was very sad about him losing this match.
"Kaybetmesine" denotes the act of losing tangible items, in this case 'keys', showing an occurrence and the reactions to it.
Onun anahtarlarını kaybetmesine kimse şaşırmadı.
No one was surprised at him losing his keys.
"Kaybetmesine" implies losing abstract items like 'plans', with emphasis on the impact and subsequent action.