2004 Other Toyota Models how did this happen?

You bet your ball bearings the mechanic screwed up. My guess is either he/she forgot to torque the axle nut or just forgot to install the nut all together. Glad you are alive and able to write this. Since your life and your investment (car) was put in jeopardy, demand compensation for any work done on your car that led to this, as well as repairs to it after the incident. Hint on a settlement to help you forget this ever happened and help you through this troubled by economy times. After all is done, go to a better place for further car service. Good luck.