lost property

noun2

1. •
   Property that is found in such a state as to make it likely that the original owner unintentionally ceased to be in possession of the property, and would be unable to locate the property.
2. •
   (UK) A help desk or department in a store, mall, or other such facility where customers who have lost an item can inquire as to whether it has been found and turned in; a lost and found.

   • Lockwood is the junction for the picturesque branch to Meltham, where an old lost-property book recorded the finding of a "bow with two arrows" in a train, in 1873. — 1951