The 340 is out....again.....

Exactly how many cam bearings were damaged, and if not all, then which ones?
The missing plug, as noted, just redirects oil to the filter. The cleaned oil re-enters that very same passage, just above the plug.
BUT
I don't recall if there is a step behind it to prevent it from being driven in too far. I remember on my build to pay particular attention to the exact location of that plug. I do not recall a step. In fact I drilled out all those passages before it went to hot-tanking.Those as well as most or all of the others. If that is possible, the plug could find it's way up further into the main gallery, where it would severely restrict oilflow, which would only become apparent with rpm. The pressure would remain the same,as the oil pump went into bypass, while the volume would stall.With the inadequate oil-flow,the hydrodynamic wedge would collapse. 70psi oil pressure could blow that plug right down to the end of the horizontal passage, or more likely,up the vertical passage.
I would make every effort to find the missing plug. It may not be missing at all.