I think it's perfectly fair to decide to sell on to a friend instead. It's annoying to you, yes, but you haven't taken any sort of hit apart from a bout of disappointment. If the shoe was on the other foot, and a good mate of yours suddenly decided he wanted an item you're selling, I doubt very much you'd just refuse him. If you did, that wouldn't make you a very good friend.
I think it's perfectly fair to decide to sell on to a friend instead. It's annoying to you, yes, but you haven't taken any sort of hit apart from a bout of disappointment. If the shoe was on the other foot, and a good mate of yours suddenly decided he wanted an item you're selling, I doubt very much you'd just refuse him. If you did, that wouldn't make you a very good friend.
I think a "deal with it" GIF is in order here.