If you find that your Don't Starve Together items are not displayed, or are missing from your Steam Inventory, this means that the option for hiding the items are enabled on your Klei Account.
To unhide your Don't Starve Together items on your Steam Inventory, log in and visit your Klei Account User Info page and look for the "Hide Steam Inventory" button on "USEFUL LINKS"
In the Hide Steam Inventory part of the page, un-check the tick box "Don't Starve Together" as putting a check on it hides your DST inventory on Steam. Once the tick box is un-checked, click on "SAVE CHANGES" to complete the process.
From there, log out of Steam and then log back in and you should find the DST items listed in your Steam inventory.