Dodgy Letting Agent

Tenancy Deposits

My ex-letting agent told me that my tenants deposit has been lodged with the DPS, however she did not receive a certificate??? Is there any way I can check that this deposit is indeed with the DPS. If this letting agent is not being entirely truthful what can I do to get this deposit back, the only reciept I have is her signature on the AST agreement for the deposit paid. Incidently when questioned re- prescribed information, she did not know what I was talking about!!!!!!
Please advise