ah ok. Seems strange alright. As they are a broker though, its possible that its up to the Supplier to up-hold their end of the transaction (i.e. have the car you ordered!), which they clearly haven't. If cartrawler have paid the agent for the car then they need to get the money back.
I worked in a car-hire place when in college years ago, and to be honest I pity them, its absolutely thankless work; nearly every rental has some problem or other!
Its like Ryanair: when it works, it works well; when it fails, the wheels come off completely
EDIT: by the way, which website did you book it through? the brokers provide the booking technology to the websites, who in turn book the car with the Avis, Europcar or whomever. I've always found those websites cheaper than the rental agents own websites, but I guess you get what you pay for