I wouldn't have been surprised if they had known about the 'flaw', but didn't mind it, because, as Srivastava said "it wasn't worth the time to abuse the flaw". In similar vein, I once randomly generated 2 million out of 40 million possible codes. Consumers would buy products, obtain a code and it would allow them to 'buy one, get one free' for some other product. The code being short and without the usual mixup candidates (I, 1, O, 0, etc.) was much more important than people 'cracking' the system. Even at half the price, the other product still sold at a profit and nobody saw room for mass purchase/reselling.

Of course, later in the article it appeared that people were abusing cracks in the system and reaping the benefits, so it doesn't apply to this case. I just wanted to note that sometimes business concerns trump all actually interesting parts of a problem :/