Rear wheel hub assembly

Question: I have a 2004 2-wd XL-7 37,348 miles, original ower.

I felt a grinding when applying the brakes at low speed. Assumed it was the rear brakes. 3 days and an estimated 40 - 50 miles of stop n go driving later, I was traveling at 65-70 MPH the driver's side rear wheel became dislodged from the car. Lost all lugs, snapped off two studs. Dealer is telling me that a wheel mounting stud had worked loose and pushed its way back into the brake assembly (the grinding) which caused the wheel failure. Setting aside someone loosening or over tightening the stud (at this time I have no reason to beleive that this has occurred), have you ever heard of a wheel mounting stud "working" its way loose?

I personnaly have not, I have heard of studs failing by snapping off due to age/fatigue. Any comments

PS: I attempted to purchase the rear shoe brakes to replace, but found out that the rear shoe brakes are a dealer only part for XL-7's and my dealer had closed before I could buy the parts.