EQ sparingly, and try adding a little reveb - it will bring back some of the frequencies you lost. But at a cost.
Either that or just remake the whole tune using it as a guide. You may find that you make it even better the second time around.

I had a whole computer die on me, and had to do similar once. Its pretty cool - you redo what you did then but using everything that you know now, you might be really suprised and happy with the results you can achieve now.