Rick leaves Beale's office with his metal arm. Later Thorne goes to Beale's office and finds the arm. There is nothing anywhere in between about how the arm got back in the office.
After the big explosion releasing the poison gas, Rick is shown wearing a piece of cloth over his mouth for several minutes, while fighting off walkers. When Michone used a piece of cloth to cover her mouth while she quickly found cover in a store in Gone (2024), she almost dies and it takes her a whole year to recover.