This is an old thread, but it does serve to emphasise the importance of backing up important data. Electronic devices and storage can, and eventually will, fail for one reason or another. Any data that doesn't exist elsewhere will be lost - indeed, Schofield's Law predicates that data that doesn't exist in at least three places doesn't exist at all.
There are cloud services that will back up photos automatically, as long as you set them to do so. Dropbox offers a small amount of space free and is a useful way of transferring pictures to a computer if you install it there as well. Google Photos offers unlimited free storage in what they call "high resolution", which isn't the same as full res, but is adequate for most purposes. I use both so that I'm not relying on just one.
Contacts on an Android device should be sync'd with Gmail and should restore when you sign back into the device.
Other files need to be copied manually and, again, Dropbox and Google Drive are convenient (and can both be used as intermediaries for transfer to another device).
Android has no undelete option so, if you delete something by accident, it's gone. There are, however, recovery apps that you may be able to use. The first thing is not to use the device until you've tried this, to avoid the space occupied by the lost file being over-written. This means not even installing the undelete app. Instead, find something that'll run on a PC, install it there and then connect the phone by cable. Run the program and set it to scan the phone as external storage and you may be lucky.
There are also data recovery services which charge according to the complexity of the job (some can even work with a shattered hard drive), but they're not cheap. Backing up is free.
