Is there any way I can get my ferret back?

Some how my ferret got outside and my neighbors found her in their yard and so they decided to keep her, they didn't even try looking for the owners, and they probably saw the missing ferret posters I put up but they still didn't call. I didn't find out they had her until just recently, but I lost Amber about 4 months ago. The reason I think it's her is because it looks EXACTLY like her with the same markings and everything (my friend saw her.) Plus Amber is kinda rare color (dark silver with blaze and creamy undercoat with a brown spot above her left leg.) And they told me when they found her, and it was on the same exact day I lost her. I understand why they would wanna keep her because she's the best ferret in the world and she's so sweet and smart and loving, but I've had her for two years before them and spent thousands of dollars on her, and they practically abuse her and know absolutely nothing about ferrets.They keep her in a rabbit hutch outside, and it's completely inappropriate because I live in texas where it gets really hot during the summer and ferrets will get heat stroke in temperatures above 85 degrees farenheit, but they're too stupid to know that. They didn't even take her to the vet and I'm sure she has fleas by now! I went to their house and told them I lost my ferret and asked if I could see theirs because it might be mine, but they made up a stupid excuse and the mom lied and said they actually got her at petsmart when before she said they found her. Petsmart doesn't even sell ferrets!!