So Peter Stumpf has his priceless Stradivarius cello back, thanks (apparently) to the benevolence of a woman who was ready to turn it into a CD rack. But why won’t anyone at the L.A. Phil, Stumpf included, answer questions about the incident? Simple embarrassment might be part of the reason, but some observers speculate that the owner of a valuable instrument is much better off if the world doesn’t have a lot of details about what harm may have come to it. In fact, the world of high-end instrument dealing is so shady these days that it doesn’t seem unlikely that the Philharmonic might be hiding some of what it knows about the case of the stolen cello.