lost property 
noun British
A place where lost articles are stored to await retrieval by their owners.He used to steal leather jackets from department stores and hand them in to a lost property office until he could legitimately claim them as his own....
- With the new season underway, the first items of the season have been deposited in the lost property dept.
- Bosses at Blackpool Transport were among the first to give scheme a kickstart after donating 48 handsets, worth £240, from their lost property office.