Here is few options you have if you launched the game and now your account or items are lost.

Check Mail

Right down corner of main screen click on mail icon and see if you got any mails with your items in it.

Customer Support Response

Customer Support answers bug report of one of players: [https://steamcommunity.com/app/2943650/discussions/0/601898176917594814/#c601898278747937231]

Dear Player, please refer to the following instructions regarding account linking:

If you are linking multiple accounts with game data, you will be asked to select the account with the game data you wish to use. Game data from unselected accounts will become temporarily inaccessible after linking. Rest assured, we are working on providing updates so that you can re-access the temporarily inaccessible game data in the future.
If you do not wish to link to other platform accounts, please close the page. You can link your accounts later by going to "Settings" → "Link other platforms".