I don't have any suggestions. I have the same issue. When I restart my phone, I get a screen sometimes that pops up on reboot and says that it's scanning and optimizing my apps and warns me not to remove the battery before optimization is complete. It's about a 5 minute process. Then, when my phone is done optimizing and I unlock my screen, all the apps I have on my SD card are gone! There is an icon of a grey Android robot with the name of the deleted app underneath. When I try to click on it I get an error message saying "This app is not installed." When I go to my settings to view my apps, none of the deleted ones are there. Even Google Playstore shows them as uninstalled when I look them up. With time, however, the missing apps begin to appear one by one. It has taken anywhere from 2 minutes to nearly an hour in order for all of them to reappear. So bizarre! And extremely irritating! The first time it happened I cried because my photo gallery was gone and I thought I'd lost all my precious photos!