The owner of the building, Jurgis Vilutis, told Reuters that he thinks a postal worker probably searched the letters for money and hid them.
When the letters were found, Vilutis said he reached out to the post office, who decided to try to track the recipients down.
“I’m so happy they got interested,” Vilutis told Reuters.
According to the outlet, the letters were from pen pals or relatives who had moved out of Lithuania, which was part of the Soviet Union at the time.
After months of tracking the recipients down – since street names and numbers have changed –, post office workers in Vilnius were finally able to deliver only a few of the 18 letters last month, according to Reuters.
Five recipients were found and in some cases, post office workers delivered the letters to the children of the intended recipients.
“We felt a moral duty to do this,” Deimante Zebrauskaite, Lithuania Post’s head of the customer experience department, told Reuters.
“One lady compared the experience to receiving a message from a bottle thrown into sea,” Zebrauskaite added.
One recipient, Genovefa Klonovska, received a letter from a pen pal in Poland that was stamped in 1970, when Klonovska was 12.
The letter included a handmade colored rose and two paper dolls, according to Reuters.
“I thought that someone was pranking me,” Klonovska, who is currently in her 60s, told the outlet.
According to Reuters, Klonovska doesn’t remember her pen pal and thinks their relationship ended when Klonovska never got her letter.
“So good that the letter was inconsequential,” she told Reuters. “The loss was not life-changing.”
She added: “What if they delivered a lost letter from a suitor to his love, and their wedding never happened?”