Just had Sears cancel an online order that was 'in stock' when we purchased because they can't fulfill it. Did they ever have it in stock? Did they just run out

Just had Sears cancel an online order that was 'in stock' when we purchased because they can't fulfill it. Did they ever have it in stock? Did they just run out and have poor inventory control? Who knows, but they couldn't fill it when they implied they could. Not sure I'd call that unethical.