Why is almost the only queries I get about my car ad ask if it's stil available
Most people like to know whether it is worth spending time looking at. If it's not available is not worth even thinking about. If people always took their ads down when their car sold there would be no need to ask if the car was still available. If a person texts me about availability of an ad I will ask a follow up question to increase/gage their interest.
Add the text "if this ad is still up, then the car is still available." Sadly this won't stop those who remain persistently illiterate.