This is an extremely frustrating aspect of this site! You spend a good amount of time mapping a run, then it asks you to login to save it--which i do, but the process of logging in apparently loses all of the work of creating a map (with no warning). Also new maps get lost if you use forward and back buttons, the page locks up... I like the features of this site, but i really have the feeling that it's not created with users in mind, more like an experiment in web apps. Please fix these useability bugs!
I'll second this one - I've used this site for a couple of years and love it. Just created a username so I could save routes... but if I build a route, then attempt to log in so I can save it, everything is lost.
I guess it is part of the learning curve, but what a painful lesson to have to learn.
I have found this issue but the solution is to either log in and then create your route or if you are just playing around and decide you want to save the route but have not yet logged in hit Save Route. It will then ask you to log in and save all in one step. If you just log in it starts you on a fresh map.