Robux has a lot of abuse, so is more likely to deny a legitimate transaction as a false positive. He probably used his own credit card first, it didn't work, and then used his backup card, the corporate card, instead. Then claimed it as a personal expense and paid it back.

Corporate cards are generally set up to allow this. If you're traveling on company business, there's a relatively high chance your personal card gets denied. Especially when on corporate travel -- if you use the corporate card for airplane, hotel and car, the personal card use for souvenirs looks a lot more like stolen card use. Companies don't want employees inconvenienced while on company travel, so they allow use of the company card for personal expenses as long as the expenses get properly claimed and paid back.