3.3.3.B.7 has your answer I think Nick. It says Prepared and Modified cars need a 1 quart tank, but they probably expect only those cars to have the OE one removed.
So, you have to have something, but even the old Windex bottle will pass as long as there's little chance of leaks before it gets there. And definitely check your coolant level, I'm sure you're low now.
Also, if the tube to your catch tank doesn't go all the way to the bottom, then your system won't syphon the overflow back into the system when it cools down. But that just means that next time you reach that temp, it won't overflow again.
That's why you never noticed any overflow spillage- it only happened once and you missed it then.
On the dyno maybe?