You are not alone. My little man just turned a year old. He too has gone through the sudden loss of memory. I would tell him to sit or down and he would look at me like it was the first time he had heard the words. He has separation anxiety, so recall was never really an issue, but lately, as he gains his confidence he is blowing off the come command. We are in Agility training and he gets the zoomies something terrible. When we are working on our own, he's perfect, but give the guy an audience and he becomes this big show off. It's annoying.
I would say to keep steady on your training and not give up the treats. Keep the treats going until he regains his memory. Then back off the treats. Like giving him a treat for every third sit so he's not sure when a treat will come. Make him work for absolutely everything. Work to play, work to eat, work to go in the car. Make nothing free. Eventually, he will come around again.
Jericho is still on the prong collar. I've been trying to get away from it, but he's such a better dog on it that I'm not sure he will ever get off it. LOL
Anyway-that's my two cents.