Gas Cap Warning Light
 

Last Wednesday my gas cap warning light came on after I got the car washed. I checked the gas cap and it looked like it was worn out, so I purchased another one and put it on. The light has not shut off yet and I talked to a Ford Technician and he said the car needs to go at least 10-15 miles in order to reset. I'm not sure about this. I replaced the gas cap yesterday, so I've given it about 20 miles and still no reset. The technician also told me there shouldn't be a vacuum leak (all of the hoses were pretty new). What gives?