there are two interviews with the race doctor available in Swiss media (one on Blick's website, one during SRF's coverage today), and he said that both riders were located inside the streambed. He also mentions that after resuscitation they checked Mäder (as well as possible) for broken bones before his transport to the clinic, and weren't able to locate any obvious injuries. So he assumes that he suffered from a traumatic brain injury. So in the end, to me it sounds like one rider was probably just more lucky than the other.
According to him, they were stopped by a commissaire and a spectator, btw, so that should also exclude that any team car was present already at this point.