Fascinating story, may be entirely accurate or not as far as I know, I have zero idea and would have to look it up, but nothing in this write up sounds unlikely.
Salt mine: nothing weird about that. Most of the art and artifacts and documents had ended up in mines by 1944, and as far as I know more because of US/British bombardments than because of approaching Russians. (Though the later were certainly feared to behave just like the Germans had done in Russia.) I mean, did you see photographs of Berlin in the spring of 1945? Dresden? Any German city above mid-size? Nothing, including marble coffins, would have survived that. Mines and tunnels deep in the earth were just about the only place where works of art could survive without being reduced to rubble as the majority of houses on the surface were.
Re: Operation Bodysnatch
Salt mine: nothing weird about that. Most of the art and artifacts and documents had ended up in mines by 1944, and as far as I know more because of US/British bombardments than because of approaching Russians. (Though the later were certainly feared to behave just like the Germans had done in Russia.) I mean, did you see photographs of Berlin in the spring of 1945? Dresden? Any German city above mid-size? Nothing, including marble coffins, would have survived that. Mines and tunnels deep in the earth were just about the only place where works of art could survive without being reduced to rubble as the majority of houses on the surface were.