new cam-valve /lifter tap. Help!

Just had a new cam and lifters installed, CompCams XE268. When I left the mechanic and went to the parking lot to get my car, I noticed a light tap when I started it. After leaving the shop and driving 1/4-1/2 mile, I know my lifters are fully pumped up but I still hear the tap. Not ever having a new cam installed before, I did not think this was anything to be alarmed about as he must have heard the tap too when he pulled it out of his bay, after the break in. My first call to the shop was not returned. I called again yesterday and spoke to the mechanic who did the install. He started talking about contacting CompCams in case a lifter was not functioning properly. I was kind of speechless and figured they were not as interested in the noise as I was. When I first went in, I asked if he put my lifters back in the box in lobe order and he said "no, if you sell the cam, they should buy new ones." Needless to say I was not happy. Is it possible that when he dismantled the top end all the pushrods went into a cup? Aren't they supposed to be matched to the specific rocker when you reassemble an engine just like a cam and lifter are? Not to mention the $800+ installation bill. Is this a noise I should be worried about or is it just a rocker with a little too much lash? The cam that came out was 454/475 lift. The one that went in was 477/480 lift, so no big change there. I am afraid to drive it. I know there are a lot of experienced engine builders on this site. Your advice is appreciated. Please help.