Definitely have to do a dead pixel test. But too bad it's best done at home.
Take a shot with lens cap on at different shutter speed (slower better)
and then upload the pictures to your pc and either look at it full blown or use some dead pixel detection software. Or you can also look at it from the LCD and then enlarge the picture and scan thru them
If you can see those little red/blue/green dots, hot pixels. Dead pixels are mostly white/greyish in colour.