Hmmm... Yes also confirmed here on Win 7. If you close the MLO app, then anything left in the RTE window is lost.
It seems like it would be good to have preference Options in the RTE area to either
[ ] Commit contents on exit.
[ ] Save RTE contents on exit. (And put them back in the window when it's opened next.)
Probably there will be a small performance hit.
Somewhat related:
While checking this, I also noticed that the keyboard shortcut for the Rapid Task Entry tool does not show in the menu, like other shortcuts do...
I'm not sure that either of these is a "bug" per se. They are things that Andrey can maybe add to the "todo list" though. :-}