As a matter of fact, there is one! Fairy Tales: Bowman of Wellwood is my ( @neonthewrite) story that is entirely stand alone from Supernatural or the Brothers Apart multiverses. The first collaboration that @nightmares06 and I worked on was A Lich of Sense, essentially a crossover of our two main storylines, so the Bowman (and his Jacob) in that story experienced all of the events from Bowman of Wellwood.
As for the second question, we will just have to wait and see as Brothers Apart progresses! 😉 But, if we remember from Lich, Dean gave Bowman a business card with his phone number on it, and someone has to dial the phone for that little sprite. He doesn’t have a phone of his own.
And, Dean and Sam have actually been in contact with Jacob since the end of Lich! Jacob… didn’t quite believe Bowman’s tale, so to prove himself right, Bowman had Jacob call up the brothers.
Brothers Apart 