Poor Service

I took my car for service. Informed around 17:45 it was ready for collection and agreed I'll collect it in the morning the next day. I went in thinking it was not going to take me more than 15 minutes. It took me about two hours to collect the car which is basically signing the service report and making payment. I lost two hours of work waiting by the waiting area.

When I got to the car the Engine light was on. I was late already, and drove off hoping it was a minor thing and will turn off. On my way, I called them to inform them I never got through to the service advisor and left my details for a call back which I never received. Called them later in the day and requested that the car be brought back to the service centre.

A new diagnostic was run to identify the problem causing the illumination of the engine light which I completely do not understand how it was not picked up during service. How do you close off the service with the engine light on? Can I trust other activities indicated on the service report were done when the engine light that can be identified without running diagnostic was not attended to?