The project board is missing

Here's a visual of where the list of teams that you may be associated with is found:

@Leonid 

It was actually created by another person. I then worked on it for three months from November 2022 to January 2023. At the end of the project I duplicated it, copied it and moved it to my personal board.

Now in this place there is a board from January 23, 2023 (I think I created a copy of my board on that day) with the name "Untitled" and it is completely empty.

From looking at your screenshot, it looks like you are a member of an Education Plan.

When you duplicate a board, the name of the Duplicated board will be “Copy of [original board name]”, so this “Untitled” likely has nothing to do with the duplication process. To be sure, I was going to suggest that you check the Board history: Activity or Board history: Versions, but both features only store history/versions for 90 days.

can the Miro team view the history of changes and somehow restore the old version?

If the board was moved to the Trash, it would have been purged after 90 days.

When looking for the board, have you tried searching for it by name?

Also, when viewing boards on your dashboard, is your board ownership filter set to Owned by anyone?

Is your Miro account profile a member of more than one team? If so, have you looked through all of the other team dashboards? For example:

Do you have the URL/link to the board somewhere, e.g., in your browser history (try searching for the board name in your history), or did you ever paste the link to the board somewhere, e.g., in an email or a Word document? And if you can find the link, what happens when you try to load the board?

Do you have other boards in the same team that you created around the same time and that are still present, besides the “Untitled” one?

Have you only ever had one email address that you used with Miro? Because, what could have happed is that you created the board using another account that is a member of the same team where the board is, and the team settings were such that all newly created boards are only visible to the account that created them (this is called Private Boards). Then, if you were to later sign with a Miro account of which the profile’s “First and last name” was also set to “Leonid”, then it may appear that you are singed in as the account when you are not. As for the “Untitled” board, you are for sure signed in as the the same account that created the board. i.e., the board owner, as I see a “Deleted” button in your screenshot.