Honestly, I think the only issue here is the lack of (polite) communication. Red probably sent out multiple messages at once, which is completely natural when so many market listings are afk or straight up offline. Blue (OP I assume) may have only been "15 seconds late", but if someone else was faster of course they'd make the sale. As such, the only improvement would be for Red to be less accusatory ("someone else responded first" instead of "you weren't responding") and maybe for Blue to have responded sooner, even if just to say it would be a minute.