I didn't bother to check the math on this, but in the story there is not enough matter in the universe to in some way encode every possible traditional Chinese poem!
By the way, reading a "double-translation" (Chinese -> English -> Polish) is fascinating--at times it's more than obvious that what you're reading is not what the author has written, but you have no idea at all what the original concept was. (Unlike "single" EN -> PL translations, where I can often figure out the idiom or concept that was used in the original.)
In fact if you formally describe how you generate the permutations that's one of such encodings of these permutations (and the optimal one - see Kolmogorov Complexity :) ).
So there is definitely enough matter to do it. Similarly we can encode PI despite it having infinite number of digits.
Ce-ci n'est-pas une remarque, and all that.
Forget PI. Let's take 1337. Or is it MCCCXXXVII?
Is it 2 or 1.(9)? Or 10 (binary)? Different encodings, same number. Some encodings are just less optimal than others.
Same with text. Is the poem in utf-8 and utf-16 a different poem? What if you zip the file? These are just encodings, and there's no point ignoring the good ones (which for non-random strings are usually programs).