If your vehicle somehow automatically sets the air on recirculation, then that might be another cause.
I’ve had this happen to me a couple times where I’d set the temp and fan speed when I get out of the car in the afternoon and I know it’s gonna be cold in the morning. I set it so I can just use my remote starter and let it sit for a couple minutes while I finish getting ready for work. When I set the “recirc” button a time or two, I’ve had the ice on the inside of the window, and nothing on the outside.