Definitely fireworks, my cats aren't happy either

Fireworks? I think cats can hear more of them than we can.

Our cats are usually very independent, but when the July 4th fireworks started up, they now wnat to be next to one of us all the time.

It does sound like something spooked him. Glad he is getting better.

I recommend a vet check before you go.
You’ll be able to relax, and everything will be ruled out.

He seems to be doing better since I posted this. He's out and about at least. Still pretty jumpy though.

I'm guessing loud noise related.

Heath was alone during a severe thunderstorm just once - and went from ignoring storms to hiding from anything perceived as thunder.

I'm guessing each time Munchie is hearing a firework - it's setting him off again.

You know your cat best though. Maybe set up a hidey box with a blanket in it. It might help. They seem to take comfort in those when scared. (Small cave like confines).

It was the ghost he saw. Probably just got shook by the fireworks, you have no idea what happened while you were gone. My dog was noise shy, but only when she was alone, then would take quite some time to settle once she felt safe again. If it doesn't get better soon, it might be vet time.