Do not drive until the head restraints for all occupants are installed and adjusted properly.
See Head Restraints.
Chevrolet Cobalt Owners Manual. Replacing Restraint System Parts After a Crash
WARNING:
A crash can damage the restraint systems in your
vehicle. A damaged restraint system may not
properly protect the person using it, resulting in
serious injury or even death in a crash. To help
make sure your restraint systems are working
properly after a crash, have them inspected and ...