That's not true, @Dark Light . When computers 'delete' files, they don't disappear. They're marked as ok to save over. This is how file recovery tools are able to work. If your files haven't been saved over, you can get them back.
I know on Windows you can use tools like Recurva. Unfortunately I don't know of any mobile apps. @Enterprise , you can have a hunt around online for some but if you're not confident, I'd take it to an expert as soon as possible. The earlier you do it, the better your chance of getting your stuff back. Note that there's no guarantee you will get them. It's just luck to see if they have been saved over or not.
Also keep in mind that your files could be partially saved over. If that happens, they may come back corrupted.
In saying all this, if you have a recent backup or restore point as Baby Luigi suggested, I think that's the best option. These recovery tools are a last ditch effort option.