It could just be a stock response. I had several messages saying 'do you still have this item?' And when I spoke to the person afterwards, they were really friendly. So it MAY be a stock response that facebook provided.
However @percheron67 I do agree that some people are a bit rude and useless. I was giving away - GIVING AWAY - some stuff some months back, (various items,) and I had around 7 or 8 people contact me. A couple of them wanted me to take it to them, even though it was FREE, and would have costed them £30-£40 to buy.
When I said they need to collect it, and it shouldn't be too much trouble, as it's only 2-3 miles from me, they said 'doesn't that work both ways? It's also only 2-3 miles for you to bring it.' 
Instant block.
Also, I have had several people say they are coming to collect something, and not turn up. I wait all afternoon as they say they will come between one and five p.m, and they don't. At half five I message and say 'are you still coming?' Within half an hour they say 'oh sorry can't make it today, can I come tomorrow now?!' 
So I waited for four fucking hours, and they couldn't be arsed to let me know they weren't coming. I have had this happen with five different people in the past half a year... and three of them didn't even bother letting me know they weren't coming, I had to contact THEM!
I gave them all a second chance. Two of them did actually come the next day, but the other 3 didn't come AGAIN! So I blocked them after that. Bastards. 