where is lockscreen photo stored

[plzr]

i have the 3gs on 3.1.2 in one of my previous updates and restores i lost a bunch of photo's out of the camera roll, one was set as my lock screen. i never changed my lock screen in fear of losing this pic. i've tried to find this pic but cant seem to find it. so my question is where would a user photo set for the lock screen be stored if its not in the camera roll.

****edit****
it seems like after of months of looking i would only find it after i would ask for help
'
~/library/lockbackground.jgp shouldn't of been that hard to find with a name like that

[dhamien]