I have had this happen with all kinds of things on craigs list.
Last year I was buying a couch off some guy and I arranged a time to pick up an everything and then day of he called me right before the pick up time and told me someone came and picked it up the night before....I always thought that when you say ill take it and then arrange a time to pick it up that the seller would have enough class to not sell it to someone else.
A few months ago I found a 180 with stand for like $100 dollars and then the same thing happened....people on craigs list have no class.
What I have learned from this is when using craigs list is don't expected anything until its in your car on the way home.
It goes both ways. Having sold stuff on forums and on CL before, you have just as many folks backing out at the last minute or not showing as you have cases like this. When you want something gone, you want it gone.
I can't express how annoying this is... you get a ton of hits/emails on something, the first person tells you they'll be there to pick something up... you email 4 folks back telling them it's spoken for... you schedule, but the person is "busy" and will be there tomorrow/next weekend.... (wash, rinse, repeat)... they don't email back.... they never show. You're set back two weeks and lost legitimate interested parties because you tried to be a patient seller. It's a wicked pisser.
When you want something on CL... especially if it's a sick deal, you need to go there immediately to pick it up.
No offense to the OP as I don't know the circumstances. Just speaking from some of my experiences with getting burned trying to be the nice guy.