what do you mean you can't find it? Where are you looking for it? It's in the root of the card, under the "nandroid" folder...
You can always RUU and re-root, but that's usually a last resort. If you've just rooted, and are still on stock, then just make a new backup, and it'll show up on the card again.
As for partitioning your card, that's only useful if you want to use apps2sd. and apps2sd isn't even necessary, in my opinion.