Sign Language? Mute's can communicate through body language, signing, and some even go as far as to wear small writing boards around their necks. You'll figure something out.
@Leolycan Thing is, Arthur didn't start out mute, he became mute when he got Bard powers. So it's very unlikely that he knows sign language. The two options are that he either writes everything down like you said or he texts people.
An announcement; I think I will allow people to post more frequently to drive the plot along quicker. I really am looking forward to getting to the next day and all!