yup. more than likely the heat caused by direct sunlight along with the heat the camera produces itself fried the sensor in some way.
a maven @Newshound did a little test on something else, but having a camera in an older un-protected window got some interesting results.
I was rather shocked at how high that got. He got an interesting result out of it too, that overheating basically caused the camera to black out until it was within a correct operating temperature. so I have no doubt that having it in the window somehow affected the sensor causing your issue. on an odd point though, I have a couple cameras in less than prime locations for heat and sunlight protection and I haven’t had any issues…yet.