Re: missing content sims 4
The most common reason this happens is logging into the wrong account. By this I mean, you have 2+ accounts being used on a PC either by you or you and other members of the household. When you get onto the PC and use your code, it links that code and game to that account permanently. So say you have Hogifu and Hogafu as your two accounts....you go on and log into Hogifu and use the code on it...so you now have Sims4 on Hogifu. Months later you go onto Origin and log into Hogafu and poof, no game there, and the code was used already(on Hogifu) and can't be used again. This is by far the MOST common reason for this to happen.
You may also check into whether Origin has a filter set up on your games to only show installed games, or in some way hid the game. You can also try to reload game library under the games tab on top of Origin app.
Now, it SHOULD show in history all transactions for the account, if it doesn't show up the activation on that account, check to see if it is by any chance on another of your accounts. If it isn't on any of your accounts, you can Contact EA official help site and chat with an advisor(use either online chat or phone options). They can then take the code numbers and track it to which account it is linked to and related emails and such. EA Answers forum is a player to player help forum and thus can't do this for you.