Lafos is right darth.Don't want to burst your bubble but there are plenty around.Doesn't sound like you bought it though, just saw it.They have some amazing ones out there don't they.I'd like to get one some time too.
If you thought it was the real deal at first, the rule of thumb that I use when I see things like that is: If it is not from a reputable seller like The Earth, Brian's Toys or from a known member of these forums, I assume it is fake.
There was another thread that talked about the Rocket Firing Fett a few weeks back. In that thread, one of the veteran members (I can't recall who it was, Chris G.?) had tracked all of the known examples over the years. He said that there are only 55-75 known examples, which is higher than I thought. Even still, there are not that many available, so the cahnce of ever owning one are slim even if you have the money. Becuase of this many people have become very good at making customs of these things over the years.