Search your pc for the mixpad PROJECT file. The PROJECT is an exact copy of what you made the first time. Once you find that, keep it's location in mind and open Mixpad again.
Use File, open, then direct it to the PROJECTS location. if you find it, open it and WHALLA it should be the one you did the first time.
For future reff, when you close a Mixpad proj and it askes if you want to save it, always say yes (you can delete later) but make sure you remember where PROJECTS are going to be saved, and name it with the word PROJECT in the name so you will know what it is later when you are in this kind of situation. If you deleted it your s.o.l, but restore may help if it's that important to you. Good Luck