I am playing on Single Player.
I had trader Rekt who had the Crucible Schematic on day 1 in his inventory for sale.
I played for few hours and then I quit the game to do some stuff in real life.
When I got back to the game, I was unable to find the crucible schematic anymore. The trader had the same inventory but the item was just gone.... The Trader has not restock as it's only day 3 and it's restocks on day 4.
It happened to me several times, items form traders inventory just item disappears when I quit the game and restart. And usually it is the useful items.
Fix your game it's so @%$#ing annoying to get an item just disappearing. I stooped playing for now cause I am so @%$#ed.....