They opened the bottle and discovered the note had been written in 1996 by a girl named Joanna Buchan. The letter said the bottle was thrown into the water from a fishing boat off the coast of Peterhead, about 800 miles from where it ended up.
The letter, written as part of a school project, featured the author's opinions on school, her dog, teddy bears, her "rather big house" and other subjects.
"By the way, I hate boys," the letter concluded.
Haga found the bottle in 2020 and tracked Buchan down on Facebook, but she didn't discover the message request until this week.
"I vaguely remember doing a message in a bottle at Peterhead Central School that we sent off Peterhead in 1996," Buchan, who is now working as doctor in Australia, told BBC Scotland.
Buchan said reading the letter was a window into her own young mind.
"When I read it, I just died laughing," she said. "There's some really lovely lines in there, like what was important to me at the time. I wish I could tell my teachers of the time, whose idea it would have been."
Haga said she was happy to have finally connected with the message's author. She said she is not the first person in her family to make such a discovery.
"My father also found a message in a bottle when he was about 5, and he's 66 now, so that's quite some time ago, but in the same area," she said. "So this is like it's normal to have things washed up on shore, but it's not very often that you find something with this kind of significance."
