Unfortunately, there are a number of things that could cause the loss of your in-game progress or "savegame".
Steam players, fortunately, may still have their progress saved on Steam's servers. To check, load up Race The Sun, go to the in-game Options screen, and click the "Reset Game" button. If you have progress backed up it will say something like "It looks like you were previously at level X…" Clicking "Okay" at this point will restore your previous level. Clicking "Cancel" will proceed to the game reset.
However, if you are not playing through Steam or there is no saved progress, please create a new ticket to let us know about it.