I need to buy Minecraft again?!?!

No, you never have to repurchase an App, unless you changed your Apple ID. Apps are forever tied to the Apple ID they were purchased under. If you did not change your Apple ID do the following:

Open the App Store App

Tap the the photo circle at the top right of the page

Tap Purchased

Tap Not on this iPad

Find the app, which should have a cloud icon next to it

Tap the cloud icon and it will download to your iPad

As rbrylawski mentioned, reach out to Apple support. So, here is some contact info, to do so:

Contacting Apple

Contact Us - Choose Locations

USA: 1(800)MY-APPLE

Can never find what? Did you do what I posted? If you purchased Minecrast using the Apple ID you use on your iPad, the app will be where I suggested. According to iTunes, you need to be running at least iOS 8.

If it's not in your purchased library, then you need to reach out to iTunes Support for more help. I've never had an app I paid for disappear, which couldn't be downloaded again using the directions I provided.

You didn't answer my question. Did you do exactly what I posted you should do?