Custom Brush via Define Brush Preset - Where did it go?

HELP!!

I created a custom brush by selecting an area (Marquee) and then

EDIT | Define Brush Preset and gave it a name. I have been using it fine...then I loaded new brushes and it is now gone....Where does PS CS store my custom brush? Do I need to recreate it? How can I recall it?

If you replaced your brushes set without saving the previous one, I fear that the new brush is lost. I suggest going to the preset manager, highlight the new brush(es) then click on the "save set"button to save them to a new set, and protect them from accidental deletion...