Blocked account, is it possible to retrieve the conversation?

Hello,

I have a friend who wanted to share photos on Snap with a girl from his school. She agreed and also said it was okay for him to take screenshots. But a few days later, she filed a complaint against him saying that he forced her and that she didn't want him to take screenshots. My friend, in a panic, blocked the girl and she did the same, and he left his account and logged out. He would like to retrieve the conversation to prove that he didn't force her to send them. Is it possible to recover the conversation?