The game isn't storing every possible combination of a tomb reaver in memory ahead of time. You can ask the computer to generate a random number between
0 - trillion
0 - quadrillion
...
etc
that doesn't mean the computer is holding all the numbers from 0 - 1 quadrillion in memory. Doesn't mean the computer can't generate 999 trillion, or that the number "doesn't exist" because it exceeds 32 bits.
A perfect tomb reaver (likely) doesn't exist for the same reason that running a random number generator from, say, 0-one quadrillion will almost never give me back a nice number like 123,456,789,101,112.
I'm not saying you're wrong, just a thought:
Example 1: All PRNGs have a period. Suppose that I have an PRNG that generates a random integer between 0 and 1, and a period of 5. Suppose the entire period of this PRNG is {0,1,1,0,0}.
You can use this PRNG to generate a number between 0 and 15 (2
) by just having the RNG roll four times. E.g. We might get the sequence 0110 which corresponds to 6 in binary. Let's roll a few more times:
0110=6
0011=3
0001=1
1000=8
1100=12
0110=6
Then the sequence repeats. So even though we have an RNG capable of generating numbers as large as we want, we never rolled 15--and never will.
Example 2: Even if the period is large, that still doesn't guarantee every number will be chosen (or even be equally likely to be chosen). Imagine a PRNG that gives the sequence {0,1,0,2,0,3,0,4,0,5,0,6,...}; the period is huge, but half the results are 0.
Conclusion: just because a PRNG can generate a random number from 0 to 123 trillion, doesn't mean it will ever output all of those numbers. It's not just Tomb Reaver either. Some rare items that you could cook up with legitimate stats just
can't spawn,
ever.