Lost and found
From 35C3 Wiki
The lost and found is handled by the cloakroom team. Ask for your stuff or contact them via email email@example.com. In case of contact via email please be patient as they will process your request not before the end of January. The team of volunteers needs to recover from the congress, the tear down and the aftermath.
They will then sort through the boxes of found objects, prepare shipping and then start responding to email.