To help understand what is happening, I want to define some terms so we are all speaking the same language. Since I cannot duplicate what I think you are describing, I need to know more.
Mouse - that’s the thing on your desk. It never disappears. 8^) I need to know the make and model of your mouse, and I need to know if you have installed any third party mouse drivers. If you have, does your problem persist when you uninstall the third party mouse driver? One way to check this is by booting in Safe Mode.
Hardware cursor - this is the icon drawn on the screen. It is an OS X feature, and does not “belong” to Rhino. For example, Rhino for Mac cannot change the location of the cursor like Windows Rhino can. The hardware cursor always moves exactly in sync with mouse movement. The icon might change when crossing view boundaries or when starting and stopping commands.
Rhino cursor - (I’m being a bit pedantic here) - when drawing geometry like lines, there is a second, smaller cursor inside the hardware cursor. This cursor does not stay perfectly in sync with mouse motions, but might snap to grid lines or to a nearly object snap. When the hardware cursor moves far enough away from the snap point, then the Rhino cursor will catch up with the hardware cursor.
Other input devices - If you are using a tablet, of course we need to know that. If you have more than one input device plugged in, of course we need to know that.
One more note: although Rhino can never change the location of the mouse cursor on the screen, it can (and mouse drivers can) change what the icon looks like and can also hide the cursor. For example, when the cursor moves from one viewport to another, it briefly changes from what Rhino has set to a split view cursor for changing the size of viewports. Or, if you move the cursor into a dialog box, the cursor changes to an arrow.
FYI, Rhino never deliberately hides the cursor, but some combination of factors is causing this to happen.
So, in light of the definitions above, is the hardware cursor disappearing, or is the Rhino cursor disappearing?
When the cursor disappears, what was happening at that time? Was the cursor crossing a viewport boundary? Did you just finish a command, but the cursor was always clearly inside a single viewport? Remember that this is only happening occasionally for you (and never for me) so there is some edge condition that you are triggering to make this happen. Try to observe and figure out what that edge condition is.
Third party mouse drivers let you customize a lot of behavior and that may interfere with Rhino. What happens if you uninstall the third party mouse driver and use Apple’s built in mouse driver?