Rookie mistake....you did good starting out with some home brews before leaving the house, but you forgot to have a couple resting in a cooler in the trunk for just such emergencies. Your learning my young jedi.....
Never go to a party empty handed. You can always position it as wanting to "contribute to the party", even when it's nothing more than making sure you've got a real beer to drink. I've made beer friends that way, as you'll have people come up and ask where the real beer is!
Miss Manners says to always show up as a guest with something. Bottle of wine, six pack of the good stuff, or a plate of brownies. You'll never miss an invite that way!