Hi, can you give more information about your issue? What were you last doing ingame? In what way is your progress gone (file not showing up, showing an earlier date, etc.?)
I've had some issues before with stardew valley not noticing my save file. If on android, try to backup your saves manually. They're probably in /sdcard/Android/data/com.chucklefish.stardewvalley or some similar path.