Searching for document ID with KM API

Hello,

I have copied documents manually in KM via webdav. Now, I am trying to access KM with KM API and to change the displayname.

My problem is that the documents appear in KM. but I can't find them with KM API.

If I create documents in KM, I am able to change the displayname.

It looks like, that the property displayname is not filled.

Is it possible to search for the document id or any other idea?

Can anybody help?