My ESN was stolen from my phone, now mine is bad, and the thief's isn't?

I am new to this whole ugly business, so I am a little confused as to how this works. I'm a sprint customer. Now, it's not like I was happy with them before, and when I reported this to them, they were as useless, rude, and as stubborn as they always are, but I don't understand WHY and HOW this happened.

I sold my phone to someone in Virginia. I am not the original owner of the phone, but I bought it directly from the person who was. I decided to sell the phone on eBay. Yes, I put the DEC number on the listing, to prove it was good. However, I assumed, if YOU DON'T PHYSICALLY HAVE THE PHONE, they can;t attach it to a phone, and if someone tried to, SPRINT, could track them down, as I can prove I am the owner of the phone.

But according to Sprint, and their fraud department, it's "whoever gets to a phone first with serial number, wins" philosophy.

Financially, I am now SOL. But I am morally outraged. How is it possible, that my legitimate phone with the legitmate ESN has now been "dirtied", while the thief, has the "clean" ESN, and gotten away with it. Sprint has the ability to track it down, but they won't. In fact, when I reported it today, and the person I sold it to were both pleading with Sprint at the store, I was treated with near contempt. Can someone make sense of this for me? PLEASE?

By the way, I filed a complaint with the FCC on Sprint.

I have had my ups and downs in the past too. Their customer service isn't the best that is why I left them. I am sorry you had this experience with them. My brother had them and they sent him a termination letter because he was using up too many roaming minutes even though they knew when they signed him up that he would be roaming. My suggestion is to stay on top of the complaint that you filed to ensure that your voice is being heard.