So, it is not clear to me that BTC could be counterfeited successfully at all. Yet, I DID read something about "counterfeit Bitcoin" somewhere and am curious.
As it stands the protocol will not allow it and the multi-petahash mining network enforces it.
More likely they were referring to fake Casascius Coins which are physical coins with a public key on one side, and a "tamper-proof" holographic label on the other that can be removed to reveal a private key.
Check this thread for more info: https://bitcointalk.org/index.php?topic=49817.0
Yes, Likely it was fake Casascius Coins. Mike discusses it here:
Beware of Fakes on Ebay
Enjoy,
-MikeMark