Broken (missing) part on Pivot Arm in rear suspension

[pip]

I discovered the loops (2x) welded to the Rear Suspension (front) pivot arm completely GONE. I've got about 900 miles on it so far.
I'm not sure how this could happen?
Any ideas...stud heads hitting? (nah)
see pics...

 

[maxdlx]

$hitty welding from the factory

 

[pip]

$hitty welding from the factory

It doesn't look like bad welds, it appears to have good penetration, there's even some of the parent material left behind...