It’s possible a wire was loose at the receptacle from the beginning, and having it plugged in for, seems like longer then you usually do, caused the arching which causes the heat and melted your electrical box. If you had a GFCI breaker it would of tripped sooner. I’m not sure if the make combination breakers with AFCI/GFCI for 30amp plus receptacles. Just change your breaker to one of those, see how far back your cable is fried and put new receptacle there. Keep us updated!!
It’s possible a wire was loose at the receptacle from the beginning, and having it plugged in for, seems like longer then you usually do, caused the arching which causes the heat and melted your electrical box. If you had a GFCI breaker it would of tripped sooner. I’m not sure if the make combination breakers with AFCI/GFCI for 30amp plus receptacles. Just change your breaker to one of those, see how far back your cable is fried and put new receptacle there. Keep us updated!!