Paislee Shultis was cowering in a “tiny wet” compartment when police removed wooden boards at the house in Saugerties, New York State.
The youngster was reported missing in July 2019 after being taken with her older sister from their parents by officials.
Police found her in “good health” on Monday, after a tip-off – with mother Kimberly Cooper alongside her.
Dad Kirk Shultis, 32, Cooper, 33, and grandad Kirk Shultis Snr, 57, were charged with custodial interference and endangering a child.
The girl has been returned to her legal guardian.