am sad and very pissed with myself

So, it's 99% confirmed I've lost my Rebecca Minkoff MAC laptop strap. I've made my sis check everywhere I can think off and she can't find it. Which leads me to conclude I've left it on the plane. What has me so pissed is I'm usually very anal about checking stuff before I leave. I was particularly hurried that day and that has potentially cost me my strap. Ugh, I'm not liking me so much right now :(