You're right that the reaction products will clarify much. I bet the mixture is opaque to UV and the DSC pan and the DSC itself were most certainly opaque to UV. So the light could have been there, just not observed because of its surroundings. At this point it's very possible that another theory could explain the result, but Dr. Mills' theory is the one I know most about at this time, and I am unwilling to give up his classical approach at this time to go back to alive and dead cats and seas of quarks. But if you prefer another theory, let's explore!
That and possible interesting H/metal interactions that do release a lot of energy should be considered if strange elemental findings are reported. The serounding mass may absorb and have an opaque attitude to the spectral products.