I think what made this especially easy for them to ticket is that it expired in December 2014, and now it is 2015. All 2014 stickers were black, the 2015 ones are green. A quick glance shows it is out of date.

Glad it was a truck so had commercial plates where the sticker is on the front not rear plate. I imagine if it was a car with the sticker on the rear plate I would have been pulled over by the police.