It's fascinating that you saw the young man come out of the fireplace. It's not something you would expect, is it? (Unless you're a Harry Potter fan.)
But in the Celtic/Druid tradition, it's not so strange. The fireplace is seen as the living heart ("hearth") of the home, and the spirit of the family lives there. Not only that, it's a place where you communicate with the dead -- it's sort of an altar to your ancestors. This is where you would put pictures of your dead relatives, and where you would put offerings to them -- especially around this time of year, Samhain (which became Halloween).
In the Celtic tradition, it's extremely common to see spirits of the dead around a fireplace -- especially, of course, the dead associated with that hearth. Did you ever find out if that young man with the backpack was associated with that house?