Popular? I see the same 6 people talking about it.
The data is permanently gone, accept it and move on. Blizzard have said it is gone and they only keep backups for a few months, the item restore system proves that. Data recovery only works if the data isn’t overwritten.
The only thing I see Blizzard doing wrong is not sending out any emails about it. But if you were active during this time you would have seen that it was available.
The only other thing I could they they could have done was to activate the characters in both versions but that would have those who paid for the service up in arms about it.
The Classic Era version of the character will be permanently deleted and unavailable for cloning.