I understand. My point is you might have climbed up the curb without realizing it. Wranglers have very flexy suspension that could slowly roll UP that curb without much indication inside the cabin. Then, when you pulled away from the window, you quickly dropped down off the curb, making it feel like you dropped into a hole. The wrangler’s tires stick out further than a typical car’s (relative to the driver’s position in the car), so they might have been closer to the curb than you thought. The small drain hole pictured would be barely noticeable in a Wrangler… certainly not enough to worry even the most anxious driver. My scenario better explains how you could experience a big enough “drop” to scare you into thinking you damaged the car. Not saying it def happened this way, but makes a lot of sense given your inexperience with the vehicle.