ISX 2014 in a Freightliner

[madtruckeroutlaw]

GM, I have a 2014 Cascadia with a ISX in it. The other day truck regened heard a weird noise under the valve cover injector side, pulled cover couldn’t see anything, went 2 a dealer across the street(didn’t tell them I pulled the cover) they said a flatten rocker or something. I said thanks and picked up my load haven’t heard it since. Truck runs good, oils good, coolants good. As of 1100 miles still haven’t heard the noise again?? Should I find someone and do some test or not sure what to look for. Thanks Paul