Ipad Pro 9.7, 256gb

I think there maybe a glitch in the program on saving.
My painting didn't save after I finished for the day yesterday. I am always in the habit of pressing save often while painting then before closing going to the gallery to check its there. When I opened the program today it displayed that the program had closed without fully saving, consequently all the work I had done yesterday was gone. The last time it happened I thought it was my fault maybe closing without saving.