When you've marked an item as "sold", the item disappears from the list of Manage items and My Shop.
If you're a member of TradonoClub Basic or TradonoClub Premium, you can access a view of the items you've sold on Tradono.
Under My profile > History, you can see a list of your bought and sold items, so that you can keep track of your sales and purchases.
Please note: If you've mistakenly marked an item as "sold", we can always help out and reactivate your ad. Contact us through the "Get help"-button in the app, through our Facebook-page or at firstname.lastname@example.org. We're happy to help! :-)
Related article: How do I mark an item as sold?