djmtsu,
Well, it's not really a test for emissions, but a test for the fuel system pressure. This is why you often hear of people's check engine light going on if they fill up the car with the engine running.
From what I understand, that error code should clear up after starting and stopping the car a few times.
Now, keep in mind the manufacturers motivation here. How much money is made when the car is sold? A grand? Maybe two? In most cases, money comes at service time. If an error code is thrown that your gas cap is loose, how is that going to bring people into the stealerships worried that their engines are on the brink of dying? The only solution we have is to rely on places like AutoZone until they are forced to stop reading the codes or buy our own code reader. My wife's car is a 1996 Civic, so I know I'm going to have to buy a code reader at some point.
Bogatyr