I have a sort of fondness for the guy, and I'd like to think he's a person of his own. It is possible to carry a stick and not hangout in a grave yard when you were little, and just because you are in the same place as somebody else was seven years ago and are into the same kind of things doesn't necessarily mean you're them.
My theory is that the Poe Salesman, finding an excellent supply of poe specimens decided to remain in Hyrule after years of travel. These years of travel left him with just a walking stick and his tattered clothing. When he arrived at the guard house he found that there was the dead body of a Hylian Guard, who had formed his own collection of Poe souls, and decided to make himself less conspicuous by adding to his outfit a sash bearing the triforce, which he had seen in a few other places around. He also found near the guard's dead and decaying body a hurriedly scribbled triforce symbol on parchment stuck to the wall, undoubtedly left there by a frantic guard in a religious frenzy. He also made use of a local stock of alcohol, which, in combination with near starvation, leave him delirious and in no state to chase his poes. Upon meeting the hero of time, he decides to make use of this sturdy young man and pays him with the piles of unclaimed rupees he found lying around the market.
But hey, that's just me.
