I honestly think you can make a GOOD argument for them re-instating you as a "gold premiere." It's not the phone number that they take into consideration. It's the account! As long as the account was under your name for 10 years, I'm positive you can have them look into that.
For different reasons, I've had to change my number 3 times, since I've had my account. The two (2) secondary lines that I have on my account have been with Sprint for 12 years, but only been under my name for the past 6 years. The end of this year was supposed to be my 10 year mark, but they waived that considering the 2 secondary lines had been with Sprint for 12 years already, even though the numbers were connected to a different account before.
When you call them, I'd just mention the old number that you had and old account and see if they can make an "exception" for your case in being a loyal customer that has come back.