How can I be charged with a DWI if I was never even in the car?

I went to San Antonio to celebrate Cinco de Mayo. I took the Greyhound Bus from Laredo, TX. I chose a hotel 5 blocks away from the bars so I wouldn't drive, just walk back to the hotel. I went to the bar and of course drank cause I was not going to drive. So when the bar closed, I went back to the hotel when this car pulled over, a dude got out and assaulted me. He got back inside the car and drove off and he crashed with another vechile then he took off running. When the police came, they charge me with a DWI!! That's not my car, I was not driving, and I'm just worried. I told the police what happen they told me that I was just lying to them trying to get out of a DWI. But there is a traffic camera on that street, wonder if that will help.