If you didn't sign an SWA3 (Rent Supplement application form) but the CWO received one, which they would need to begin the claim process, then it was signed by someone else.
Yes, it is a legal requirement for the HSE to pass on to Revenue details of Rent Supplement paid along with the landlord details supplied on the SWA3. So it's likely that your details (if they were entered on the SWA3 form) have been recorded and sent on for 2009.
Since late 2008, landlords have been asked to supply their PPSNs - this was done by way of separate letter, sent directly to the landlord following the award of the Rent Supplement claim. If your name & address was supplied as the landlord details, then a letter was issued to you.
The HSE could not give you details of another person's claim (even if it is family, and you are involved, albeit without your knowledge). You could write to the CWO (or to the Superintendent CWO) to advise them that you are not a landlord and have never signed any SWA3 forms in respect of the rented address. This would start an investigation into the claim.