The Reddit user, who goes by the name of bestmattever, uploaded a photo of a hand written letter from a girl identified as Evie, KPIX-TV, San Francisco, reported Wednesday.
In the letter, Evie said she accidentally brought home two sticks -- which were attached to the note -- from her time as a junior ranger in the park.
"I know I'm not supposed to take things from the park, so I am sending them back. Please put them in nature," Evie wrote.
Bestmattever said he wrote back to the girl and her parents, commending her for her honesty and promising to put the sticks back in the park.
The letter was trending on Reddit on Wednesday and has received more than 7,000 likes on Yosemite National Park's Facebook page.