When an item(pages,microflow etc..) is in the repository (i.e) committed and when you delete an item, the changes pane will display the deleted item.
When an item has been added locally and not in the repository(i.e) not yet committed, the changes pane will not display the deleted item
You probably deleted an item that had never yet been committed. In that case, it is no change compared to the latest commit.
If you delete any document that has previously been committed, you will see it in the changes-pane.
The deleted item may not be a part of the committed version of the app, so it was not shown in the changes pane
Changes pane only show changes of those items that were committed earlier and are now modified