Q: i restarted my phone and multiple apps that i use often disappeared. i tried to go re-download them but in the app store it just says "open" instead of download, like i never even lost them. What do i do??

You have also tried a reset (not a restart)?

Reset: Hold the Sleep/Wake and Home buttons and don’t let go until the screen goes dark and the Apple logo appears (no data will be lost)

Do you sync with iTunes on your computer?

If you do, try syncing.

A reset usually resolves this issue. If that is not the case you may need to backup and restore iOS.

iOS: Back up and restore your iOS device with iCloud or iTunes

If restoring from your backup does not resolve the issue then the issue may be present in your backup in which case you will need to resore again and set it up as a new device.