It's surprising that I won both battles, even though my main stack skipped its turn without its action being displayed in the battle log.

I already wrote that it's quite possible that different players will have different battle outcomes due to desynchronization.

Make it a habit: if any disconnection occurs, especially in battle, and even more so in the final, IMMEDIATELY TAKE A SCREENSHOT so you can prove your case if necessary.

I've never seen anything like this before.

Just because you're seeing something for the first time doesn't mean it can't happen; you should IMMEDIATELY contact the judges instead of badmouthing your opponent. (This applies to everyone).

P.S. I'll take a look at the saves, but I don't think it will help.