I dont know whrther it caused by virus or the system, or the photos are just hiden by virus. If it caused by virus, u can use the antivirus software. and after that you can see the hiden photos, but if the photos are deleted by virus or other reasons, you need the professional data recovery software. And I know one named Easeus data recovery software, my friends use it and I always get helps from them and the software. at least, in my cases, the lost data was found completely. u can google easeus and you can find the official website. It seems the software quite famous. I suggest it if u dont have methods to deal with it.