I closed a "tab" (pane? window? not sure the correct term) within my screen session. Is there a way to recover a "tab" lost in this way?
(not dissimilar ctrl+shift+t in a browser)
No. Once a shell session has terminated, it is gone, no matter whether it was running in GNU
tmux, in a terminal emulator or directly on a console.
A web browser is different as it's able to just reload the page in a new tab if you ask it to reopen the most recently closed tab. A browser may additionally keep track of data that you may have entered into forms etc. before closing the tab, and restore this too. GNU
screen does nothing of that.