As a user myself, I get where you're coming from, Grouik Petitgoret.
You bought Minecraft Java back in 2011, still have the original purchase email, and the terms at the time said you would not have to pay again, all of which you expect to allow you to reclaim the license. Believe me when I say you're not the only one ever stuck in this situation.
However, "the license" here is linked to your Mojang account, and unfortunately, cannot be transferred. Even in some exceptional cases, you would still need access to the original purchased account (which needed to be migrated to a Microsoft account before 12/18/2023):
- If the license was not migrated before that deadline, Microsoft current guidance is to purchase Minecraft again, as Support no longer handles account migration requests.
- If you already migrated the old Mojang account to Microsoft, you would need to recheck:
- Make sure you're signing into Minecraft Launcher with the account having the migrated license.
- Visit Minecraft and sign in > check if the profile page displays your Minecraft: Java Edition profile.
- If that account no longer shows ownership of Java Edition, this becomes an account/entitlement issue.
- You can then contact Minecraft/Microsoft Support. That's when the purchase email and ID can be helpful.
So in short, your chance of getting the license back depends on whether you migrated the Mojang account, and still have access. I know this is not the answer you were hoping for, especially given the terms under which you originally bought the game, but there is no official way to restore an unmigrated 2011 Java license.