I had a similar thing happen myself. Strange thing was, after pulling the head off, it turned out that one of the valve seats had dropped out. Luckily it was caught by the valve and wedged back into the cylinder head. Damage was totally confined to the head.
Being honest, I'm a big fan of RLTC, and I had it on my car for 8 years, equating to around 40-50,000 miles in total. Never had any issues with engine damage, and believe me, I used it!
For what it's worth, IMHO, a built engine is only as good as the builder. I had a built engine in my car, built by Mig. I would like to say I helped him build it, but in reality, I just helped bolt bits together. He was very anal with clearances tolerances and cleanliness. That engine never missed a beat.
Good luck with your findings. Hopefully, as in my case, it won't be too bad.