Unidentified perpetrators in Mainhausen near Offenbach had bricked it up during the night, police told local media.
It could have been built within minutes, they said, and the motive is unclear – possibly a joke, an act of revenge, or a bet.
Police are searching for several people. The damage to the property is estimated at €500 (£425).
“That went up pretty quickly, too.”
But he added: “It’s a crime and no joke.”