While the "tone" is not rude, the fact that they are quite deliberately ignoring his questions is rude.
It's not YOUR job to provide them with numbers. You know for a fact that what you said is true - that SSC is not fulfilling orders in the order they are receiving them. At this point, all you should be expected to do is bring this up and then the onus is on THEM to start providing answers.
It is THEIR job to go back into their own system and figure out which orders were placed, when they were placed, when they were filled, and how and why they screwed up. If they need order numbers, fine - then THEY can check THEIR OWN records, because I'm sure they've got all the order numbers logged in their computer!