If you no longer have the truck meaning that you have already received settlement for the total loss and signed the truck over to the insurance company that paid out your claim or if there was no insurance to cover the claim so signed the title over to a salvage yard to get rid of the totaled vehicle than yes, normally you could now cancel your insurance on the truck.
You do not want to just ignore the insurance payment bill but will want to contact them and let them know that you no longer have the vehicle due to the total loss and thus no longer need the insurance policy for it. Being canceled by the insurance company for non-payment instead of canceling out the policy yourself would look bad on your part and may make it hard to find auto insurance in the future so that is why it is important to cancel out the policy the right way.
Now if your total loss claim is still being settled than you may need to continue to pay on the insurance policy for the truck. Most insurance companies advise that you should not remove a total loss vehicle from your insurance policy until you are no longer using a rental vehicle and your damaged vehicle is no longer registered in your name. The vehicle is usually no longer is your name at the end of the insurance settlement process when you sign over the title to the insurance company and receive your check for the actual cash value (ACV) of the vehicle.
In many states, an insurance company will be able to remove the vehicle from your policy retroactive to the accident date when you are ready to take it off of your policy. You should discuss with your insurance provider at what point they would advise you to remove your coverages from the totaled vehicle and if they can make the cancellation retroactive or not.
Keep in mind also that if you take insurance off of the vehicle while the registration and title are still in your name than your state may penalize you for a lapse in car insurance. When the plates and registration are turned over to the insurance company or back to the state's DMV than you usually can take insurance off the vehicle without any issues arising.
If you have more questions about your total loss vehicle or claims procedures regarding when you will sign your truck over you can speak with the insurance adjuster working your claim or try contacting the consumer division of the insurance regulator for your state.