I got mine back a couple years ago by making a side account with the email address I used on my main account. Post on the Neopets facebook page daily too. I had mine frozen and got it back after about 4 days of posting daily on the fb page, posting daily on the ticket waiting forum, and updating my ticket every day. It doesn't sound like I have a typical success story, but that's what worked for me.
Basically what happened was after the AC in I think 2016, my account was hacked and all my NP and red codestones from my SDB were taken. After the four days, TNT restored my account, gave me my NP back, and extra NP to cover the cost of about 100 red codestones (on average).
I don't and never had premium, so I hope others have good ideas for that. No one ever said anything good about it, so I felt it wasn't worth it.