Once a Sketchfab model is deleted, it is no longer being indexed by Google. However, Google can still show the model URL as a result. Clicking the search result won't show the model, but it will be a matter of time before the Google results no longer include it. Unfortunately, Sketchfab cannot change Google results.
Why is my deleted model still in Google search results?
Explanation of Google indexing delays and URL removal for deleted Sketchfab models.