What happens if car is totaled in chapter 13 but no claim was filed for the car?

A car is not totaled in a chapter 13. A car may be totaled while the owner is in a chapter 13. If the car was fully exempted, nothing happens. If you need to buy a new car, you will have to get permission from the bankruptcy court after you file a specific purchase agreement (car loan) which should not seriously affect your plan payments. Why are you not asking your lawyer?