It's been years but I did help someone with a trapped mouse. They couldn't move the mouse from the left screen to the right screen. What was it? I had them move the mouse to the left until it showed on the right screen.
That is, be sure to try moving the mouse off the trapped screen on all sides.
This is a weird one, but I hope someone has advice. I've got a mac mini and set it up with two monitors. The taskbar keeps jumping from the main monitor to the secondary one, and I'm beginning to think what I think is the main monitor isn't, but I know how to go into the display arrangement and drag the taskbar back to the correct monitor. However, I was in the display arrangement screen to move the taskbar today and instead of moving the taskbar, it moved the monitors. I know how to fix that, too, but it froze while doing it and left the monitors in a diagonal position, instead of the normal side-by-side. Now my mouse is trapped on the wrong monitor and my systems preferences only comes up on the other monitor. I can't get to the arrangement display to drag and fix it. I can't plug a mouse into the other monitor, rebooting doesn't help, tried to copy the systems preferences to trash it so I could get access but that didn't work. Any suggestions? Thanks in advance.