HOW TO UNDO DELETE PATTERN

I accidentally deleted a pattern from one of my libraries in creative cloud.  I briefly saw a transparent popup that included an undo button.  This vanished as I was moving to click it.  CMD+Z (I'm on mac) did nothing, and I see no menu option for undoing anything.  There is surely a way to undo what i just did other than the now-vanished popup.  Please tell me where i can find it.  The attached screenshot is the view I had into the library when this happened.  I would like to sarcastically thank Adobe for hiding this feature, and for allowing one-click deletion without a confirmation click.