When I tried to open it, WinRAR prompted me for a password. I tried everything—his birthday, the dog’s name, the coordinates of the workshop. Nothing worked until I noticed a faded inscription on his old drafting table: "In Retrospect, do Only Justice, Riley."
The specific term does not appear to be a known creepypasta, ARG (Alternate Reality Game), or widely documented internet mystery. A .rar file is a compressed archive format created by WinRAR. IRdO-JR.rar
Do you have or a specific source where you saw this file name? Knowing where it came from could help identify if it's part of a specific game or online puzzle. Need to open, create, or convert a RAR file? - WinZip When I tried to open it, WinRAR prompted me for a password
Based on the cryptic nature of the string, here is a complete short story centered around that specific file name: The File in the Attic Need to open, create, or convert a RAR file