Landlord did pay back deposit but did not use DPS

[Soapie]

My daughter and her friends had a flat under an Assured Shorthold Tenancy. They have now moved as the AST finished and they have had their deposit returned. The Landlord appears to have not used the DPS and did not confirm anything to them during their tenancy. The landlord has been asked if the DPS was used but no reply has been forthcoming. Using the DPS was included as a clause in the tenancy agreement. Can I check retrospectively, if the DPS was used in an archive somewhere? Is there a case for compensation by taking the landlord to court if the DPS was not used or would this only apply if the deposit was not returned?