How do I fix data loss on a flash drive (more in the description)?

Question

Java

There is such a problem. I create a folder on the flash drive and (from the first PC) I drop text files into it, insert the flash drive into the second PC, open the flash drive, and the folder is empty (when deleting the folder on the thief's PC, it gives an error).

ps And I need to fix the error so that without third-party programs, since I open the flash drive at work.
I will give all additional information in the comments. Thank you.

Answer 1

Your operational part is not heavily loaded (creating, changing, deleting user tasks), since the user does not have many tasks themselves. There are only 24 hours in a day and only 365 days in a year. A much greater load falls on searching and filtering the list of tasks (or cases, as you call it).
A possible solution would be a multidimensional representation of the data. For example, in a star schema : there is a task table and several dimension tables that can be sampled (user, task type, project or task category, meeting place, date and time, etc.). This requires some denormalization and more overhead for operations on individual records, but makes it easier to aggregate and select lists.

Answer 2

https://www.piriform.com/recuva
but keep in mind - most likely there are no files there
and feel free to bring a USB flash drive to work, like at your place "it was read before, but then suddenly ..."