I don’t think I’m a Marriott apologist but there’s no way I can condone what OP did. And then a bombastic post “shocking IT fail”, “imagine my horror” etc etc. I think is an over the top reaction to what OP admitted was lax behaviour on his part.

Now I don’t do all the things that CLEguy does. But at the very least I never close my reservation booking page until I get a confirmation email. And it has nothing to do with Marriott - any airline, OTA, hotel etc. it’s all the same. Check if I’ve received the confirmation email. Then close browser/app. With so many players being involved in a transaction anything can go wrong.

OP traveled to another country without this basic check and got stuck. He doesn’t have my sympathy. Had he got a confirmation email that for some reason Marriott didn’t honour... now that would have been different.