I want to sell some tf2 items on the Steam Market, however, my inventory seems to have vanished, that is, the tf2 tab is no longer there. After I noticed this, I decided to try selling through the tf2 backpack itself, both to make sure that I hadn't actually lost my items and to see if I could actually sell them. I did have my items, but when I select the "sell on Market" option, it just sends me to the first item in my Steam inventory.
This was the situation as I began writing this question. In order to write it as accurately as possible, I performed my actions in tf2 again, only to discover that it is now working. I then went to my inventory on Steam and (after refreshing the page) the tf2 tab is now there again. What could have caused the tab to vanish and then reappear?