Undo Close Tab in Vim

Your file is probably still open in a buffer:

:ls " get the buffer number
:tabnew +Nbuf " where N is the buffer number

To reopen buffer 18, for example:

:tabnew +18buf

I'm using an MRU (most recently used files) plugin. So I can edit the last 30 files I've just edited

Here are the MRU plugin metadata:

File: mru.vim
Author: Yegappan Lakshmanan (yegappan AT yahoo DOT com)
Version: 3.2   Last Modified:
September 22, 2008

Usage

To list and edit files from the MRU list, you can use the ":MRU" command. The ":MRU" command displays the MRU file list in a temporary Vim window. If the MRU window is already opened, then the MRU list displayed in the window is refreshed.

Simple answer is no, there is nothing built-in.

But a workable solution would be to use a plug-in like the excellent BufExplorer. Since it defaults to listing the most recently used buffers first, reopening a closed tab would be as simple as pressing \bet