I was sculpting my model, i was ALT LMB zooming out, and now i can’t find my model? is there like a frame, or aim, of something like that?
hi levitateme ,
This is a depth issue.The solution :
1 - While in edit mode press …t… to get out of it.Cursor changes to white circle.
2 - Pres…w… and a gizmo should pop up.
3 - Any where outside the perimater of your model and the gizmo, while pressing the left mouse button ,drag towards your self. You should see the model emerging from its hiding.
4 - Press …t… again to get back into your modelling .
The other option is to CTRL-N , clear the canvas, and redraw your model.
As I mentioned this has to do with the fact that zbrush restricts the movment of the viewing camera in the z-axis ( depth) , to accomodate the 3 mediums 2d , 3d and 2.5d…actually brilliant thinking from the zb team!!
Sometimes objects drawn on the same depth level (z value) can pile up on top of each other and cause the problem you experiencing, so what we are actually doing is moving your object infornt of them so we can see it 
Hope that helps mate …good luck with your work.
Kircho