Bad customer service

Took my 'brand new' second-hand NP200 for its second service (it's first by myself) at this dealership on the 19th June 2020. The process of booking it in went well they even send you a reminder a day before. Despite the fact that I was the first customer to arrive on the day they called me later in the day at around about 4 p.m. to say the car was ready for collection and by then I was already heading to the dealership anyway. Arrived at the dealership I was given the account for which I can say it was the most expensive amount for a service for any car I've owned, I paid the bill and took possession of the car. About a month later Tuesday the 21st July I'm leaving my work and I meet up with a friend/colleague who i haven't seen since lockdown. Him being the typical guy he walks around the car fiddling there and there he pops the bonnet. To my surprise the engine cover that was there prior to the vehicle service is no longer there. Right there and then I phoned the dealership and I spoke to a Jacque who took my details down and promised to get back to me. Thursday morning the guy hasn't called so I called back the dealership and unfortunately he's not available and this time I speak to a John he takes my details again promises to come back to me nothing happens. Friday morning I call back this time around I insist in speaking to a manager and he's not available only to be available next Monday but they pass me on to the workshop foreman whose name is Richard. He looks out the system he tells me there is a note that there is a investigation going to ascertain as to what happened to the cover and ask of me to give them time, he assures me that probably they will call me before the end of the day. It's now Wednesday the 29th of July nobody has bothered to call whatsoever with any explanations. Now I'm wondering is it because to them I'm inquiring about a lousy plastic cover or is this how they are at customer service?