The assumption that it was untested is probably an unfair one. Once a network reaches a certain size, it is very difficult to simulate it in a lab. Number of routes/updates, variety of packet destinations, different card revisions and layouts... heck, even statistically, you have problems. An issue that appears 5% of the time will only show up in a a 10-router test lab half the time, but in a 400-router network it'll pop up on about 20 routers and wreck your whole day. And when you're out of cash, you can't really afford to devote lots of hardware to a lab.
Having a lab does help you but usually (this might be different if you are WorldCom) vendors are not too interested in fixing problems you unearth in a lab but instead only agree to raise priority of issues if their boxes fail in production. I´ve been hearing that the change in economic situation has been improving the response, but haven´t tried it personally. Not too many years back, a "P2 case" could take a year to get a fix where "P3" rested in never-never land longer. "P1" worked. Pete