I'd sneak into someone's apartment and live in one of their cupboards like some sort of weird gremlin-like creature. I'd only emerge in secret to use their bathroom and to raid their fridge before scurrying back to my lair within my claimed cupboard. And on the day that I'm discovered, I'd hiss and jump out of the nearest window never to be seen again and will forever be recorded in the annuals of urban mystery.
Outside of that. I'd just make the most of the situation. Maybe fulfil my brother's prophecy of me becoming some sort of mad person living on top of a mountain or hill somewhere, speaking in tongues at random travelers. But that being said, if I had no way back into society, I'd just become a forest dweller of some kind.