(Must be my day for giving electrical advice. lol.)
What happened sounds more like a connection problem than a "reverse polarity" problem. Polarity problems should either trip circuit breakers or ground fault isolators. They don't usually create heat like that. Heat is caused by resistance. I'm betting there was resistance in your cord to coach connection and whatever amperage was going through it caused it to overheat.
The good news is (other than you not burning to death that is!) it sounded like it damaged both ends anyway. Replace that cord and connector with the best, highest amperage components you can find. For others reading this, make sure those connections are good and tight. Meaning if your cord or connections to your coach are getting a little too used, replace them. The biggest cause of electrical fires is loose connections. Shorts or reversed polarity issues "should" trip breakers. Remember, it's AC voltage. If reversed polarity started fires, all the things you plug in that only have two terminals would start on fire about 50% of the time.