You will need to check with the GAP insurer that is listed in your paperwork to find out if your coverage was intact at the time of your accident even though your first payment had not been paid yet.

If your GAP insurance is active then after your vehicle has been declared a total loss and the actual cash value (ACV) has been determined then the GAP should cover any difference between the ACV and your loan amount. If your car is not determined by the insurance adjuster to be totaled then the GAP insurance would not be used so find out if the car is a total loss and if so contact the GAP carrier to find out if your coverage had started when the accident occurred.