Thank you for your answer! Yes, apparently there's some kind of hardware problem with it, my storage disappeared just a few months after i bought it after which samsung fixed it, then the same thing happened again just days after the warranty expired. I've tried various solutions including some to remount the storage with no success =(
Well I suggest plugging the omnia into a linux machine and open gparted to see if you just screwed up with the partitions...
however, you can always follow the installation guide for internal storage, skiping instruction nº3 but the fstab part (do the fstab stuf taking care with the partition numbers)
I say take care with the partition number because it depends on the order you created them.