Loosing 100 ft lbs in that short of a time and you should be able to see the problem somewhere. You will have to pull ALL the rods and mains to be sure. If the cam spun freely when you put it in, it's not likely the problem. How do the cyl walls look from the bottom? Did you check the rotational torque of the short block when you put it together last? Should have been in the neighborhood of 25 ft lbs. How was the oil pressure? Stay positive. You will find it - hopefully without too much damage. At least you didn't have to deal with taking it in and out of the car again.