We have found the true reason for Barenboim's idiosyncratic flinch, visible on the televised versions of Teatro alla Scala's Tristan und Isolde la prima from December 7, 2007. We hear it from a good source that the rogue teddy bear was hurled @ Barenboim by one of the pissed Fials workers .
//You can find the real version here on teh utoobes @ 6:40.