Passtime

I'm new to this site but need help from others that may have experienced the same issue as I have with my 2010 Silverado which has 9,800 miles on it. After the truck sets 12-16 hours and once I start the engine I hear noisy lifters that rattle for a few seconds. I have it back to the dealer 4 times now with the truck still there but they can not dupilicate the problem. I agreed to let the truck set at the dealership since last Thursday, 10 Mar with them starting it today, 14 Mar. I've read some on the issue but can't find a recall or service bulletin from GM.