Loud buzz then "Fixed Itself" a day later?

I have a microwave question. My wife mistakenly put a meat tray that had a metal tiwst tie on it in the microwave. It started a small fire by melting the styrofoam. She noticed it promptly enough and we stopped it and cleaned everything up no problem. Right after that, we tried to use it again a couple times (making sure no metal in there!) and the microwave made a loud buzzing noise and the internal light flashed repeatedly - seemed like something was shorting out - so I unplugged right away and left it unplugged for over a day. Now we just tried it again and it seems to work totally fine - heated a cold beaker of water to boiling over several minutes. All functions appear normal. is it possible for it to simply "reset" itself and it is OK to use again?