Apple, nor any other computer company, is responsible for your data, if it becomes corrupt, deleted and/or unrecoverable.
Apple assume no responsibility for anyones' data.
It is up to the user of the computer or mobile device to take the responsibility of protecting and securing their own device/computer stored data.
NO computing company or software developer is ever going to claim responsibility for your data.
Whether you paid $10, $100 or $1000 for an application.
The responsibilty of protecting your saved data rests, squarely, with you!
Any computing device or software is NOT bulletproof or infallible!
The software and devices can glitch or fail or function erractically at any time.
If you own a computer with the latest version of iTunes downloaded and installed on it, there was no excuse for not plugging your iPad into your computer (at some point during those few years) and making a series of automatic backups of your iPad and its data.
You left your known precious, important and irretrievable data on your mobille computing device (an iPad) for waay too long and you got burned when something unexpected happened to your iPad and your application!
If you do not own a computer, it was still up to you to get educated on the different ways to backup data off of a mobile device.
There are portable storage devices designed to use with mobile devices and iDevices.
There are cloud, offsite server storage sites to store and backup data to.
Apple offers iCloud with free 5 GBs of storage OR 50 GBs of storage for $1.00 U.SD. per month!
200 GBs of iCloud storage for $3.00 U.S.D. per month.
There are other cloud, offsite server storage like DropBox that has free 2 GBs of storage that works across any mobile device or computer.
There are others, like DropBox, that offer reasonable monthly pricing for larger capacities of storage (50 GBs and up).
Plus, you can utilise more than one free data storage option at a time.
I use both iCloud AND DropBox for any data storage.
You should NOT be relying on your mobile computing device for ANY long-term data storage of important data.
These new mobile tablet devices are still, relatively, young technology that isn't robust enough, yet, to trust important data to, alone.
You need to get some sort of redundancy data backup storage plan in effect.
You learned a very hard lesson about computers and data.
But, this is NOT an Apple issue or problem or their responsibility...it is yours!
Good Luck to you in the future!