If your vehicle get destroyed far away from HQ, simply bring a squad to your car ( do not click the REPAIR option on the car or it won't work ) then your squad should manually repair the vehicle to around 10% health. You will then be able to drive the vehicle back to HQ base but very slowly.
I highly recommend that you bring an extra squad to protect your broken vehicle and other squad but that's an option.
It it gets night time before you get back to base, you can stop, hide in a house til morning and pray no one attacks you.
Hope it helps