Hi SS,
I'm sorry but we usually remove threads that are not active for more than 14 days in the "marketplace and exchange corner: others" on a regular basis. The thread you are looking for is likely to have been removed.
If you have made a transfer of $40, that means you actually have the account number of the person. Since you've the seller's mobile phone as well and if you suspect that it has been a fraud, you can lodge a police report and the police will be able to locate the person.
Regards,
Chin Leng.