You were running from security with a bag of spray paint, hood up and mask on. You were doing graffiti and got caught, you accidentally ran through a shop and into a shop district... Diagon alley. Magic all around.

you looked like a Muggle, but all of them remember clearly the legend they heard from their families, the curse that was made by Gellert Grindelwald: "my second descendant, my grandchild, will return from the Muggle world as an orphan and shall wear the family dragon heart necklace, and will the the color of the pure." Also, they could see, you looked just like him...

Now your stack in a place where you don't know where the exit is. Gl