That would make sense. This is a single wire circuit that feeds only one side of the ammeter. If the red wire had contacted ground near the meter or if that side of the meter was grounded internally, then this would have been the result. The other side of the meter apparently didn't go to ground or the black wire would have melted. You are on the correct path to cause and repair.
Doug
My memory may have failed me.
I got home from work and ran out in the dark with a flashlight. I couldn't remember what wires were cooked. I have also done some repairs so it was difficult to tell. I found a photo from
2 years ago when the carnage happened. This is not a current photo, but it gives idea what originally happened.
