You probably accidentally pressed a one of FN F1-F12 combination. A list of Toshiba FN keys that allow you to activate a range of features on your laptop listed below. The one you want is probably "Fn-F9":
# Press "Fn-Esc" to mute or unmute your computer's speakers.
# Press "Fn-F1" to lock your laptop. When you lock your laptop, only the user password you have set will allow anyone to access it.
# Press "Fn-F2" to display all power saving options available for your laptop. For example, you can turn off your optical drive to save battery life.
# Press "Fn-F3" to activate the Instant Standby mode. This mode powers down your computer except for the memory, allowing you to quickly turn on the computer the next time you need it. Instant Standby allows your computer to stay on for up to 30 hours.
# Press "Fn-F4" to activate the Hibernation mode. This mode is similar to Instant Standby except the power can last for 26 days; however, it takes longer to power on the computer.
# Press "Fn-F5" to cycle through your display options.
# Press "Fn-F6" to decrease the brightness of your monitor. Each time you press these keys, you decrease the brightness.
# Press "Fn-F7" to increase the brightness of your monitor. Each time you press these keys, you increase the brightness.
# Press "Fn-F8" to change your computer's wireless connection from Wi-Fi to Bluetooth and back again.
# ***Press "Fn-F9" to disable the mouse touchpad. Press the buttons again to enable it.***
# Press "Fn-F10" to disable the arrow pad. Press the buttons again to enable it.
# Press "Fn-F11" together to disable the mouse number pad. Press the buttons again to enable it.
# Press "Fn-F12" together to zoom in your screen. Press the buttons again to zoom out.
# Press "Fn-Spacebar" to change the resolution of your monitor. Each time you press these buttons, the resolution changes.
I hope that helps.