I deleted the photo app that actually comes pre-installed on Android and have been just using gallery. Is there any way to download the photo app?
I did this also, and found an app in the Play Store. It's called Google Photos, but you don't need to search for it that way. Opening the store and typing "photos" will bring it up as the first option. The icon looks exactly the same, so you'll recognize it right away. The download is free and easy.
My phone is a Samsung Galaxy 4 running Android 4.1.2. I may be wrong, but I think any phone which has previously had the app will be able to download it again.