That's kinda like saying, I made a document in Microsoft Word including pictures etc.. turned the PC off without saving it then when i switched it back on how comes my work isn't there?
If you have laid out samples how you want them, maybe made some tracks and a sequence too, then press the save button located on the numbers keypad, create a new folder where ever you want to save work. I have mine structured kinda like:
MPC4000 H/Drive>Songs
>Drums
>Vocals
>Multis
>Programs
So would go into 'SONGS' folder, create a new subfolder with the same title as i want to call my work, then in that folder do a 'SAVE ENTIRE MEMORY'. This will then save your chopped samples, your programs, track/sequences and Multis all in one place, so to get it back you just find the folder you created whilst you're in the 'LOAD' page, also found on the key pad, click 'Do-It' and it will load everything back to how you had it when you saved.
Sorry if this is hard to understand but I'm trying my best
