Dark Little M has primary oiling to the mains, they recommend that you donot run oil restrictors with that blk. If i were a betting person i would say you had other issues to lose a rod. IE wrong clearance, not good rod bolts. I don't know what kind of clearance you had but i always run .0025/.003 rods and mains and the best rod bolts available L19 bolts only. A lot of engine builders use the std. 8740 rod bolt that come with most rods, big mistake in my opinion, especially on a high dollar race motor.
JMO
Zip.