OMG need help fast

Sorry about the cell phone dyin!!! The funky retainer is a valve rotator on the exhaust valve. There is only 1. We were discussing why there is only 1. The engine has 2 different valve springs like the engine should have valve rotators on all of the exhaust valves but there is only one. The engine turns but the exhaust rocker dosn't move. The cam is gone or the lifter has had a massive failure.