RV mirrors stick out a bit, on most of our rigs, the better to see what's "back there." This creates an optical illusion for oncoming traffic: we appear narrower than our mirrors would indicate.
I had a similar instance a couple years ago. Towing down a narrow country road, an oncoming pickup clipped my mirror. I was all but in the ditch, he was nowhere near the ditch. Fortunately, no damage beyond both of us having to reset the mirrors.
Glad your damage was limited to mirrors, which, after all, can be replaced, and fairly cheaply at that.