Why does Katniss say that the trip to District 12 was not a complete waste?

The quote in question can be found in chapter 2 of Mockingjay. The full quote reads,

So I guess the trip to 12 wasn't a complete waste.

Katniss is referring to her trip back to District 12, which is narrated to readers in chapter 1 of the book. Katniss has returned to her district to see the remains of her hometown and the people who still live there. The entire area was in bad shape before Katniss left for the original Hunger Games, but it is nearly a complete wasteland after the Capitol's firebombing of the District.
Katniss is able to visit her home, and she is able to gather a few things of sentimental importance to her and her family. Near the beginning of chapter 2, Katniss returns to District 13 and gives Prim her cat. Katniss gives her mother a book of plants and a wedding picture. Prim and her mother are consoled by the return of their items, and seeing them this way gives Katniss a moment of comfort. Her trip to District 12 was not a fun trip, but it did give her the chance to bring those items back to her family. Therefore, the trip wasn't entirely bad or a complete waste of time.

At the beginning of Mockingjay, Katniss has embarked upon a solo trip to visit the remains of District 12, which was almost entirely obliterated by firebombing from the Capitol after the Quarter Quell's surprise conclusion in the previous book. Viewing the district's remnants allows her to witness the devastating effects of the revolution firsthand, and in her former Victor's Village home she receives a veiled threat from Snow in the form of a fresh white rose hidden in a vase of old flowers.
Rescuing family possessions from their old home is the only pleasant aspect of the expedition; Katniss retrieves her father's hunting jacket, her parents' wedding day photo, the family's book of healing plants, a blue hair ribbon for Prim, and Prim's cat, Buttercup. Upon returning to the family quarters in District 13, Katniss distributes the sentimental items and notes that "for a moment, the place almost seems like home. So I guess the trip to 12 wasn't a complete waste."