Any "money processing" organization, which would include sellers of VGCs and money orders, is instructed to evaluate transactions of $2,000 or more to see if a SAR is appropriate. That is not really a law, but some instructions from a government guidebook. So they may just gave been gathering information and no SAR was filed. Acting evasive makes it more likely to get a SAR filed and in my opinion giving a fake SSN is a bad idea. If they file a SAR using your invalid SSN, the government can see the mismatch since your name, address and Drivers License number is probably on the SAR, and that SAR will probably get a lot more attention.