After being forced to flee the fight, Graystripe is led back to the nest he has been staying in by a female kittypet named Millie he meets, who assures him that losing to Duke is nothing to be ashamed of.

After a dream in which he is visited by his deceased mate, Silverstream, and his daughter Feathertail, and another fight with Duke and his allies, Graystripe finally makes the decision to try to return to ThunderClan.

The Lost Warrior was praised by Publishers Weekly, which felt that "Many little (and perhaps some larger) girls will find this kitty fantasy irresistible".

[3] School Library Journal praised how "the "manga-inspired" artwork and panels work well with the story.

[4] Leroy Douresseaux praised both the writing and artwork of the book: "Writer Dan Jolley hits the ground running, showing the chops of a veteran comic book writer by concisely and quickly bringing the reader into Erin Hunter’s world of Warriors...artist James Barry draws in a manner that is similar to animated films.