Yes, Sokka does lose his sword at a certain point in the series "Avatar: The Last Airbender." In the episode titled "The Serpent's Pass" (Book Two: Earth, Episode 12), Sokka's sword, which has sentimental value to him, is stolen by a rough group of thieves known as the Rough Rhinos.

The loss of his sword greatly affects Sokka as it was a treasured possession and a symbol of his growth as a warrior. However, Sokka's character continues to develop and contribute to the team's efforts, showcasing his resourcefulness and strategic thinking even without his sword.