Tfl fare evasion, will I get letter?

Hello, a few months ago I was using my brothers 11-15 zipcard (it was a one off) intead of using my bank card. I am 18 and because of my height, the inspector knew it wasn't my age. He fined me and I was verbally applogetic and paid on the spot. He gave back my brothers oyster card and said that I could be prosecuted. I gave my details and he returned the sheet to me but i dont know if he recorded it or not. Will i receive a letter? What do I do? I will not do this again and have apologised to my brother already