Preferences > Desktop Session Settings missing in 13.10

[John Hupp]

I referred to this problem in another thread, but it really is a 
separate topic, so here it is on its own.

I was troubleshooting an Autostart problem and was looking for 
Preferences > Desktop Session Settings, but find that it is not 
present.  This is in a full installation of desktop i386 Saucy done 
within the past week or so.

Federico Leoni reports that Desktop Session Settings is present in his 
full install, so my initial assumption that Preferences > Default 
Applications for LXSession somehow replaces Desktop Session Settings is 
incorrect.

So the next question would be how can I fix this (and maybe also how did 
it happen)?