Passed out at work, has anyone experienced this?

I'm a 4th year medical student. I was at work a few days ago and during a mole removal procedure I passed out, and hit the ground. I've never done anything like that before. I've been in surgery many times, and delivered babies. I'm so confused why this happened. I spoke to the doctor he said I just had a vaso-vagal episode and that it was nothing. Has this randomly ever happened to anyone??? I'm scared to do procedures now.