Time Machine in Mail App

Hello,

I accidently deleted the complete content of one of my Inbox Mail Accounts. I went into Time Mashine to restore the messages, it said it was restoring but nothing showed up. I tried it a couple more times, again nothing. I know that the recovered messages should show under "On My Mac" "Time Machine". Now the funny thing is even though that folder does not show on the Mailbox List on the left when I select a message and choose "move to" it shows the Time Machine folder! See screenshot...

Now how do I make it appear on the left to actually acces it and get my recovered messages back?

Thanks!