Wait a minute, he's called himself a hero twice, but he wants the hero to visit his shop?
It was a translation mistake. I was also confused, but reread the first chapter and it's clear now that the girl at the mixer was asking, "Have you ever met a great person in the past?" To which he responded, "I met the hero."
His shop was the first place the hero visited on his journey to defeat the demon lord. At this time, the hero was level 1, dressed like a beggar, and using a wooden stick. No one believes him because they all envision the hero as a flawless entity that was always larger than life.