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??

Try a reset:

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)

Make sure they were not accidentally moved to a different page or into a folder.

Do they show in Spotlight search (swipe down from the middle of the screen)?

What apps are missing?

Are they iOS stock apps?

Have you checked your restrictions:
Settings > General > Restrictions

They do not show when you search for them?

You can try resetting your Home Screen Layout:
Settings > General > Reset >  Home Screen Layout

Do the missing apps show here:
Settings > General > Usage (it may take a second to load) > tap Show All Apps (if there are not all listed)

Try deleting them then redownload them from the App Store.

In Settings > General > Usage > tap the app > Delete App

Then open the App Store app > Updates > Purchased > find the app & redownload by tapping the cloud icon on the right

Are you sure they are not on a different page?

Try swiping your finger across the screen from right to left.