We Accidentally Put A Plastic Lid On A Pot Roast

We accidentally put a plastic lid on a pot roast that had just been browned atv400 degrees. He lowered the temperature to 215 and put the lid on. ( the kind that comes with a foil pan). I discovered it after about 15 minutes. The big lid was curled into a twisted ball. The temp was on its way down from 400. The meat looks fine, but the lid is now a small twisted ball. Is it unsafe to eat it?