The file was moved to a client project 3–4 days ago, and after that it became inaccessible.

Hi ​@Yoo Sung Hwa - happy to help figure out what’s happened.

When you say:

The file was moved to a client project

Were you the one who originally owned the file specifically, and then transferred ownership to a new person?

Or did you transfer an entire project to a new person as mentioned in this help page here?

Or did you transfer team ownership to another person, as mentioned here?

I just want to make sure what exactly was transferred, because there are different suggestion I’d offer up depending on the situation.