Southdakotas2k is right. If its an evap code, it will be a 2 cycle code to satisfy monitor criteria. It has nothing to do with mileage or time driving, but everything to do with temps, level of fuel in tank, how long the car is parked, etc..
An experienced tech can satisfy an ecu monitor in 5 minutes if he knows what the ecu is looking for.
As said before, have the codes read (though I suggest buying a cheap scan tool (20-40$) ) if it's P1456, clear it, Or just let it ride and see if it resolves itself. If its another code you'll have to dig a little deeper.