Why have my android apps uninstalled?

[AC Question]

I left my phone to charge overnight, not powering it off, but leaving it on standby, and in the morning, all of the apps on my SD card have been uninstalled. I had a greyed out icon of each one still on the home screen though. Should I reinstall the apps?

 

[B. Diddy]

Welcome to Android Central! Go to Settings>Storage​. Does the SD card even show up as mounted? The card may have unmounted at some point due to a hardware issue. Or the card might be defective or failing.