i've been trying for the longest time to find safety blanket in a run to finally get that 100% completion but it's almost like i haven't even unlocked it, i've done about 5-6 runs all the way to loop 2 just to find it and yet it hasn't showed up, getting to loop 2 lets you see 70-80% of all passive shop items so i'm not sure if it's either my usual luck in video games or something's wrong, i unlocked safety blanket using the percs pill instead of the book but i don't see why that would influence it since i still got the unlock either way

and of course after i post this i get it in the next shop, finally got 100% for real

Hope is just bad luck and not a bug, but maybe the percs pill show's the unlock, but actually not work, as the unlock say "use book of Shadows on a lost soul"

Good luck finding the blanket

Percs does unlock it normally, you were just very unlucky.