Good, that means you'll be able to take a closer look at your car and see if there are any other problems with it.  Have you looked for other potential safety issues, like lights or brakes that might be out?
assistant
It sounds like your car is safe to keep driving, and will remain safe if you drive it with the bumper falling off, since your car is at home.  We should also examine your car to ensure that it doesn't have any additional issues.  Is your car a newer or older model?  Is the car mostly driven on a highway or in a city?
assistant
My bumper just fell off. Can I keep driving my car?
user
Yes, a vehicle’s bumper is not a safety device.  However, your car might not be in perfect condition for driving right now.  Can you tell me more about the situation?  Is your car at home or work right now?
assistant
All right, so it's fine then?
user
Your bumper is one of many components of your vehicle, so if you keep driving your car, we'll want to check for other possible safety hazards. Can you say more about where your car is right now?
assistant
My car is at home.
user