Toyota Camry Valve damage?

Well, my 94 Camry ( 4 cyl. 2.2) had an oil leak, which I assumed was caused by a faulty camshaft oil seal, because the guy who sold me the car said that he had repaired that seal with some sort of adhesive (i have no idea why he didn't just buy a new one). Anyway, replacing the seal meant removing the camshaft sprocket and the timing belt, as well as the motor mounts. Once the seal was replaced, I aligned the camshaft and crankshaft according to the markings specified on the sprockets and engine block/timing belt cover. After reassembling the car, I started the vehicle and it fired up fine, and idled smoothly. Then I revved the engine and heard a rapid "thunking" sound. To me it sounded like the timing belt had slid off the sprockets or the idler pulley had failed, and released the belts tension. I did not have time to get back into it, so the next day I had it taken to the mechanics. After an hour in the shop the mechanic called me and said that the timing belt was still on and that he had done a compression test and believed that I had bent valves, and possible piston damage. I was under the impression that the design of my camry's engine was the "non-interference" type, so that timing belt problems wouldn't harm the engine. Is the mechanic just trying to rip me off, of is it possible that I could have damaged the valves by misaligning the cam and crank shafts?