The wiki currently doesn't have a specific report on Fernando Mendoza's second preseason game. The page covers his first preseason game (where he threw a TD to Jack Bech), but details on a second preseason appearance haven't been added yet.
That said, the broader story is still relevant: Kirk Cousins is expected to start Week 1, and Mendoza's role is that of a developmental backup learning under Kubiak's system. If you'd like, I can check expert videos for any recent mentions of his second preseason outing.