Hi! We’re gonna need a bit more to work with before anyone can give you a solid plan. What kind of phone you’re using: Android or iPhone? And do you remember where the photo was stored? Like, was it on your phone’s internal storage, an SD card, or synced to a cloud service?
Also, what exactly do you see now? Is it just a black thumbnail in the gallery, or is the photo black no matter where you open it? And what’s the file size, does it still look like a normal photo, or is it unusually small?
Let us know if you’ve already tried anything.