jarthur's canon point is before john knows what happened to her (or even who she is), so he found out when they both went forward in the time slipping flood
it really is a pity that Arthur and Hilbert are both the "how about we DON'T talk about useless shit like our feelings???" types because he has Very Strong Opinions about people using deals to bring back the dead
arthur opened up to john about her once in the future (in ep 17), and it got used against him so fast that he's fully resolved never to talk about her to anyone ever again
trying not to steal nat and john's thunder, hahainboxdoor.