Ok, so I decided to drive the car around as much as I could during lunchtime. I went out to my car, turned the engine on and, yes you guess it, the check engine light is back on. After work, I'm taking it to a guy who's authorized to work on Mercedes. We'll see if he can unravel the mystery. At least I didn't have to drive around for 75 miles to find out that the light was going to come right back on. See! There is always that silver lining. haha.