It's quite a big setback cos you pretty much didn't eat for a week. There is nothing you can do but just go down in weight and work your way back up. You probably won't be able to go up faster, I'd just take the patient approach as you probably lost a bit of muscle mass. Remember, every workout you fuck around and do other shit with, it's another workout you have to eventually do later on. Might as well just get on with it and work your way back up. Before you know it, you'll be back to where you were before.
On the other hand, if you are really fucking pissed about losing progress, then just switch your squat form to the HBBS. It'll feel fresh and you won't be so angry every workout lamenting your lost progress. It really does not matter how you back squat for novice, unless you put the bar right on your neck or on your erectors.