99 Eclipse Damaged Valves/Bad Cylinder Compression

Hello, I own a 99 Mitsubishi Eclipse RS 2.0 DOHC 5 speed trans with 82,532 miles on it. Recently, I had my Timing Belt and Water Pump replaced. The mechanic put the timing belt back on in the wrong position on the wheel, off by 1 tooth. He drove it up the road and back before discovering it and then had to reposition it. About a month later my #2 spark plug fowled, so I had them do a standard Tune-Up replacing the plugs and what not. Not long after that, my engine light came on and the code came back as insufficient EGR flow or possible vacuum leak I was told. When I had that checked, they did a cylinder compression test because they stated the engine sounded like it was missing. The compression test showed that the #2 cylinder was 75psi, half of what it should be and not even enough to fire the cylinder. The #4 cylinder was also deteriorating at 125psi. They said it is probably a burnt valve. My question is when they replaced my timing belt incorrectly and drove it, could that have damaged my engine and caused all this? Thanx!