Same issue here and not only with Pslam 11:6, but a few Iconic Weapon Blueprints as well as two others that were supposed to be at said location and were not.
Tried re-loads for a few of them other than Psalm and still nothing. If these drops are subject to RNG... That is beyond ridiculous and hopefully gets rectified, currently gave up on collecting anymore as i will not be able to fill the armory display and honestly that was my goal.
Like a few other missions that are not working and stopping me from gaining a couple trophies (which will now have to be done again on another playthrough & unsure if it will give me the same issue upon re-trying).
These issues, along with many, many more are really starting to not look good. Makes me wonder really how much testing went into this game in development (real / thorough testing). The more i keep pushing past 150 hours = i just keep finding broken quests + broken drops + broken trophies...
Will keep remaining hopeful that CDPR is aware + they actually care & will in time fix and rectify alot of these issues. I understand bugs and performance problems first yes, but these problems are also a concern and keep discovering more and more of them