OK, I DO NOT use iPhone!!!
But I think following MAY help
attach the phone to the computer
change to root
# ls /dev/sdb*
# fdisk -l
# mount -t hfs /dev/sdb(x) /mnt
-> if hfs is not viable, use hfsplus instead
-> where (x) is the partition of your iPhone where user's data is stored...For more information follow the link below
Probably it is 3.
Now you have got it mounted, copy anything as usual