Although I’m not new to ZBrush, for some reason, I’m having more trouble learning it that I would have thought possible. This evening I was modelling an arm in ZSpheres and doing quite well, if I do say so myself. I accidentally shrank one of the knuckles down to near nothingness, and zoomed in to correct it. The first swipe of the mouse enlarged it a bit, but I miscalculated on the second and moved the whole shebang off the viewable area. I couldn’t find it again.
Question: is there a way to “recenter” an object? Or perhaps, since I see that there is now a way to get multiple views of an object, is ther a way to get a side-view or a top-view and find the object again? Anything so I don’t have to feel like I’m flailing around in black, empty space…
Under Tool 
Modifiers you can press Unify to recenter to any/all of the XYZ axis. The new center is calculated according to the objects volume so you will most likely end up with a different center than what you started out with.
A better way of course, is to just Undo the two operations you mentioned. All tools have their own Undo/Redo list so even if you drop the tool and pick another to modify you can allways go back to the first and undo (within that session).
You could also resize the tool via deformations or simply zoom out when in edit mode? I hope that helps
Actually, in the circumstance you describe, the best approach is to exit Edit mode, Ctrl+Z to remove the copy that’s lost off-canvas, and then redraw it and enter Edit mode again.
I’ve done this sort of thing a few times, and it’s easy to get back to work. 
yes, if u mess up doing a zsphere, your best bet would be to ctrl-z, and re-do it, or if you wanna fix it, instead of zooming in, just turn the density down to zero, and it will just show the main spheres, so it is easy to enlarge … it is in like tools>modifiers, above the picture (i think, im not at school, so i dont have z here)
OK. I think I get it…Ctrl-Z, or undo…I’m going to do it this time. Thanks to you all…