Index patterns get a unique id generated for them when they are created. If you create an index pattern and then create saved searches, or visualization based on that index pattern, and then delete the index pattern, then those saved searches and visualizations won't work even if you create an index pattern with the same name because the unique id is different.
But you can fix things. If you copy that uuid from the error message (the one that starts with 68b, then go to Management > Index Patterns, and create a new index pattern (maybe delete the old one first if you haven't saved new searches or visualizations based on it).
When you get to step 2, clicked the Advanced link and paste in that uuid from the error message. That should fix any saved searches or visualizations based on it.
