So my brother was playing and while he was in dragonsreach he told Faendal to go home. Faendal then started walking towards the Jarl and opened an invisble door. My brother walked up to balgruuf to see if the door was still there. It wasnt now faendal has disappeared from the game

You don't say on what platform your borther is, so here is the solution for pc users: open the console and enter

prid 0001348C [enter]
moveto player [enter]

and Faendal shoud appear next to your player.

Sorry bout that he's ps3