I don't know I didn't write it... and probably because he didn't have enough time to, или he didn't know where she was and she found one of those emergency phone things that are on the side of the road/a phone booth and called him, but i don't really know like I сказал(-а) I didn't write it!
I think Damon knew that Klaus would back off.In my opinion they are alot alike and they understand eachother.They would both do anything for their families.It is my opinion that Stefan was playing on his(Klaus)'s weakness. He has shut off from Elena and would have killed her I am sorry.His obession seems to be Klaus and wouldn't care who is in the way.I can explain еще if needed.
Several reasons: Damon didn't know where Elena and Stefan were (Klaus was the only one to which Stefan divulged their location) and, even if Damon had found out where Stefan and Elena were, Damon would not have had the time to reach them before Stefan had finished his absurd (but effective) demonstration. I'm assuming Damon learned the location of Elena from Klaus and then picked her up. But I could be wrong about that.