Servicing Mishap

[V8 EF Fairmont]

Hi all, I would like to get a few opinions on a service 'oops' that happened to my Ford Ranger at the 10,000km service. I had the service done by the local Ford Dealer (who shall remain nameless at this point in time) and at the time was happy with the service and the price charged. However, at approximately 17,000kms I was installing air horns that I had received as a Xmas present and I noticed that the air filter cover had not been clasped down and was in fact sitting about an inch and a half proud of where it should sit. The fact of the matter is that I had been driving 7,000kms with the vehicle in this condition, over the summer months and at times in dusty conditions. Now I took the vehicle into said dealer and asked them what the story was and what they would do about it. To be honest, I had no real idea what they could do, but expected they might be able to offer something like an extended engine warranty. All I was offered was an apology, and told that they would note the error on my service record, but there was nothing else they were able to do.

What I would like in feedback, is what you think I should do from here, and what I can reasonably expect from the dealer and from Ford. Any feedback is appreciated.