Based on the context and the answer, generate a question. 

Context: I knew I should have fucking spent it on a new guitar , man ... Two weeks in a hotel though , and then moving into our apartment on Stark . I think she actually lived there for two weeks or so before she found the Boost Mobile phone I kept hidden from her that made us split up for good . And yea , it had me mum 's number saved on it .

Answer:

She felt it was used for cheating .



Why would the phone upset the girl when she found it ?