Just so no one reads this and thinks it's a good idea to tell the company to simply fuck off if the same thing happens to them:

There is such a thing as acting in good faith. When you notice an obvious mistake in your favor (even if it's made by The Evil Faceless Corporation of Malevolency), trying to tell someone about it is not only going to protect your ass if it winds up in court, it's just The Right Thing To Do.

(Of course, if they ignore you or send you in circles, then you have a stronger case that they don't want it back all _that_ bad.)