Hey 4th of July is an aweome time for everyone. You get to hang out with your buddy's mid week in awesome weather, have a bunch of beers, and let your dog off leash. Good times.
Maybe your dog is 3 or 4 and you have gotten to the point where- hey... he's not going anywhere. He's loyal. He's smart. He's not going to take off. Ok. I got it.
Here's the deal, the fire works scare your dog. They actually terrify the shit out of him- so your loyal dog runs away to escape the noise and gets lost. The animal control units know this and they are out full force that day to scoop up as many pets they can to bring them in to shelters that will charge you some ridicilous fee to get him back. That's if the shelter is organized enough to find your dog (or cat) when you actually show up looking for him.
If you want to bring your dog out with you- be responsible about it. If you're going to drink- keep him on a leash or leave him home.