Sway Bar problems of the 2009 Toyota Highlander

While driving vehicle, a snap was heard from the rear. Upon inspection, the rear passenger sway bar link (joining the sway bar to the strut) was snapped at the lower end. This link is approximately 10 mm in diameter, necking down to 8 mm with a 1 mm radius at transition of the diameters. It was observed the failure was not completely immediate as approximately half the diameter was rusted. The rust had two distinct zones; an approximate 3 mm lighter yellow-brown region at the outer side, and a 1 mm dark brown zone on the inner side suggesting the outer had been failing for some time, the inner propagating more recently. Final failure of the remaining portion was sudden. Upon inspection under magnification, the failure began with some type of crack initiating at the root of the fillet, propagating downwards at an approximate 30 degree angle. Bending of the 8 mm section appears to have been caused by the sudden final failure of the section. No other damage under the vehicle was found ruling out the failure was not caused by any driver. Toyota corporate in California was contacted (case # 1301222906) but they claimed no recall on this part or issues. The part appears to have insufficient fatigue strength or this specific link had a quality issue. The part is in my possession and available upon request should further investigation via sem/edx, or other is helpful. I also can provide pictures upon request. This failure concerns me as the part links rear suspension control and it failed shortly past warranty.