Depending on the mobile device you had (I'm assuming its a phone). Turn off data roaming and wifi just in case (so cache files dont replace existing deleted clusters) and dont add ANY more files to your device. Next, Root your device - this is the tricky part, I can't tell you how exactly to do this but if you google "[insert phone model here] root tutorial" you should be on a good start. After it's rooted (so that now you can see a directory folder when connected to your pc) you can restore the files with any data recovery program like Recuva (this costs money) while having your phone connected to your pc. You wont be able to get everything in pristine condition but you may get most of it.
Edit: Also if you are trying to recover from an SD card it will be much easier, no rooting necessary just connect it to pc and use a data restoration program targeting the SD cards directory.
Just google data recovery, there are tons of programs to choose from and some free trials.
Wow, great knowledge to share. Thanks dude, it will be great tools to those who in need.
More power, and God speed to all of you.