Following the suggestion, I checked the table restriction to roles, but it was empty.

Luckily, I retrieved the items in another way: I wondered what the table "cache" is, so I searched through it and found some historical data. Realizing it might contain what I do need, I ran a simple query

SELECT * FROM `teampass_cache` WHERE author LIKE '<user ID number>' and folder LIKE '<folder name>'

and was able to see the hidden details.

I hope this can help someone else.

Thank you for your time and efforts.

Unfortunately, I found the "restricted_to" field empty for all items. Any other ideas? I would appreciate any guidelines ...

Thanks for the tip. I will follow the steps and will post the results.