The iOS and Android versions work very differently.
Due to restrictions on iOS, we can not identify your email address or your account somehow at the moment of the purchase, so we can not send you an email with that subscription code.
Therefore, the approach we take is to save it on your device. So, in case you delete and reinstall the app, you will still have it there. But that will be lost in case you reset your device.
Please contact support as I explained before, because only them can solve this issue. With the proper information (your receipt), you will get a subscription code.
Regards,
Jobert