We have moved the Land Deed as an invisible item in your backpack. That means if you have a Land Deed in your Mailbox and move it out, you won't see it in your backpack or Mailbox anymore. It's just showing inside the Mailbox because it was not always an invisible item.
Now the question where can you see your Land Deeds? That is simple, you just have to open the build menu with P in an area you can claim the land and there you have your Land Deeds at the bottom right.
If there is no Land Deed, then you have to submit a ticket and we will check it and help you fix the issue.