help ! world lost and now merged with another!

Does anyone know how to recover my world?
I have been building a Star destroyer for 6 weeks now and I am using pocket edition on HTC m8.
Mine craft froze and I had to reboot the phone.... When I restarted mine craft my work had gone the file was called "star wars" it was on a flat world..

After looking through my list of world's there is now a file just called creative this contains my partially built star destroyer surrounded by cliffs waterfalls and trees!

What the hello happened ?
Does anybody have a solution?

Please help!

Regards