One day I go to my phone and see that my balance is 0. And I'm like.... what? That's weird.
...
I tried restoring my wallet with no surprise yet again a ZERO balance, it doesn't even show transactions at all.
So you can still log in to your wallet, but you just see a zero balance? And you were able to restore your wallet from scratch and log in successfully, but again you see a zero balance? If you click on settings and then go to "Wallets & Addresses", you can go in to any individual wallets you have created and view the individual addresses. Look these addresses up on a block explorer - are any of them your address which held the 15-16 BTC?