From a quick look it looks like they did a very neat and professional job. However, A few things that would make me wonder.
They mounted three trailer hitch receivers to the rear bumper? They probably did some bracing on that bumper. And hopefully those receivers go through the bumper and are welded to significantly more support. If the bumper has all the support, the bumper alone is not strong enough to support any trailer hitch weight. That bumper is simple cold rolled steel. And very thin walled, at that.
Of course, the other thing I wonder about is....Why on earth, did they need to raise the trailer on a lift?
I can understand, that they had the lift and the fork lift...so why not? "We do it all the time." But the "why not" would be...if not really needed...better to keep it on the ground. Should have been plenty of room underneath to do as good a job.
And to your question, Unless they crunched something in the lifting process, I doubt they melted anything without knowing it. Maybe talk to the guy with the real foul smelling shoes. Or else the guy with NEW shoes.