my guess would be that you had an excessive amount of diesel fuel fill your engine crankcase. somehow someway that diesel fuel in the crankcase exploded. the fuel was hot from the engine running...even the fuel vapor could have exploded. something along those lines is all I can think would cause the oil pan to blow off without anything hitting the pan from the inside or the outside. I would think that excessive crankcase pressure from a hole in the piston would have cause the glow plug harnesses to blow out....had to be some sort of violent catastrophe to cause the oil pan to blow off
^^^^This. IF there's truly no broken pieces this is where I would look. We actually just had this happen at work with a Cat 3406D in a dump truck because it had 3 leaking injectors, and the "mechanic" didn't want to do them, so he would just change the oil when the level got about a half-inch over the full line. He let it go too long during this last "interval" and boom, it blew the oil pan right off, created a huge mess, and scared the chit out of the driver. Your oil pan looks like its ballooned as well, one of the telltale signs.
These guys are right, there's no way EBP did that....there's too many other places that would leak that kind of pressure first by pushing past seals, etc. That was a single, large, pressure event.
I'd still look for a cracked piston or at the least a leaking injector....but that isn't EBP related.
And MORE PICS PLEASE!!!