I can find the class on SRD, but it does not list the source book.
So which book introduced Psychic Warrior?
Psychic Warrior is from the Expanded Psionics Handbook, specifically on page 24.
The reason it appears in the SRD, unlike most non-core 3.5 content, is that the XPH was released under the Open Gaming License, while most other books (aside from the "big 3" of the Player's Handbook, Dungeon Master's Guide, and Monster Manual) were not.
(An earlier version of the class was also published in the 3.0 Psionics Handbook, but this is not the version found in the SRD, and is not legal for play in 3.5, since an updated version exists.)