NVRAM is responsible for storing data and computer settings if the power is switched off. Resetting NVRAM is a common thing to try when troubleshooting your Mac. If your mouse doesn’t reappear then, try force quitting an app that you think might be causing the problem.
To do that, press Command (Cmd) + Option (Alt) + Escape (Esc). When your cursor disappears, bring up the Force Quit menu and see if that fixes the problem.
