I just entered a new post on an internal Yammer network. Writing the post took some time as it was one of the longer ones. When I tried to post it, Yammer told me that it (Yammer) had been update and needs to reload.
Result: The post was gone.
It appears as if Yammer is somewhat behind technologically. It should not lose content. GMail saves regularly and I have never lost an email that I hadn’t sent yet.
Recommendation: Use a text editor to create the post. Once you are good to go, reload Yammer, then copy the text into the browser window, and then post. This should avoid the duplicated effort of writing the post.