Retaining Greencard

So, I was married through a K-1 Visa. I am the American Citizen, and my wife left the country 2 years ago without letting us know. She had been here for 2 years, and had her green card for less than a year. Right before she left, for some reason, she gave her green card to her aunt, who we were living with at the time. When we discovered she had abandoned the marriage, I found a place and moved out. When I moved out, her aunt gave me the green card, and I placed it in my car. It stayed in there for 2 years in the glove compartment. Randomly over the two year period of me trying to track her down for the divorce, and me trying to move on with my life, she would message me over Facebook and ask for the green card. Each time she would ask she would give a different reason why she wanted it. I naturally didn't want to give it back to her because I didn't want to be a party to allowing someone who had given up their quest for a life in America to re-enter the US illegally. I know that I should have sent the card to immigration, but the investigator on my file didn't give me a clear idea of what I should have done with it, so I just held on to it.

Now, she somehow got an attorney here in America, and they have filed a criminal complaint stating that I stole the green card and refused to give it back to her. This is stressing me out, because I don't believe I did anything wrong.

The kicker here is that my car was totaled in December of 2015, and the card was still inside when it happened. Through miscommunication with the insurance and the wrecking yard that had the car, I only got a single box of effects back, and the card was not in there. They then sold the car and destroyed all the documents inside it to protect from identity theft. I don't know if my case is unique or not, but I am worried because I am just starting a career and that all would be ruined if I got convicted of theft.

Someone please help.