Why do girls privately go into our wallets searching for unknown phone numbers?

To catch your ass screwing around.

Lack of trust, insecurity, and jealousy. If I were a guy, I would never be with a girl who was this insecure. I would drop her pretty quick. No relationship can survive with such a blatant lack of trust, or with such deep insecurity that your partner needs to be constantly reassured that they are the only one. Even in past relationships where I thought someone might be cheating, I would never stoop so low as to violate a person’s privacy to confirm my fears. If I ever felt the need, that was usually my first clue that te relationship wasn’t working.