This is the 10479th most frequent Turkish word.
bulamayınca
"Bulamayınca" means "when/after not being able to find."
Here, 'bulamayınca' is used in a conditional form, meaning 'when he/she couldn't find,' indicating a cause for the subsequent action.
Kitaplığında istediği kitabı bulamayınca kütüphaneye gitmeye karar verdi.
When he couldn't find the book he wanted in his bookshelf, he decided to go to the library.
In this sentence, 'bulamayınca' expresses an action ('not finding her friend') that leads to initiating another action (sending a message).
Arkadaşını bulamayınca ona mesaj attı.
When she couldn't find her friend, she sent him a message.
Here, 'bulamayınca' is employed to connect the inability to find belongings to the emotional reaction of anxiety.