The address you send to (deposit address) is generated per account (and can be refreshed/re-generated by user), just like what normal exchanges would do.
Did you remember their address or the TX being posted anywhere?
How did you know they only received btc through 16V8yGZBKpjKBEVWUzYstP7wBr4U4MAWGj?
AFAIK, 16V8yGZBKpjKBEVWUzYstP7wBr4U4MAWGj is not their public address.
That address was shown as their address in their site when I looked. That's why I told.
Where did you get it from? I couldn't find this address in their site, maybe I didn't look correctly.
-MZ