|The following is based on Fallout 76 removed content.|
The note could be found by a skeleton at the crashed space station, slightly southwest of the torus' core, in a broken section of the station. It was removed when the station was redesigned into the Crater in Wastelanders. Although the note still exists, it can no longer be acquired.
Valiant Space Station
Airlock C7 Access Code: 111418
Behind the scenes
The access code listed (111418) written in date format (11/14/18) was the release date of Fallout 76.