Front Suspension Control Arm problems of the 2008 Toyota Sequoia

Found a large (2" dia. ) washer on the driveway at rear of the car and later a large approx. 3/4" bolt head on the driveway at the front of the car. Upon inspection of the underside of the vehicle, noted that the front bolt on the right rear control arm was missing its head. Subsequently had the dealer's service dept. Replace the bolt at a cost of about $110. 00. The vehicle had not been in an accident previously that I know of (was purchased as a certified pre-owned SUV with 60,000 miles), nor had it been subject to any hard use or rough travel, nor had it hit curbing or other obstacle during our use. Appearance of the sheared bolt head had indicated that stress cracking and corrosion had begun prior to total failure. There was no apparent damage to the control arm or the site where the bolt connects it to the frame. Conclusion was that it was a defective part that eventually failed under regular use.