When you insert a template which doesn't exists, you have the visualeditor-dialog-transclusion-no-template-description. This message says that "The "$1" template doesn't yet have a description, but there might be some information on the template's page." It is confusing, because you can think that there is a template. A message like "this template doesn't exists" would be helpful.
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Change 349370 had a related patch set uploaded (by Jforrester):
[mediawiki/extensions/VisualEditor@master] MWTemplatePage: Show a different message if the template doesn't exist
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Change 349370 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@master] MWTemplatePage: Show a different message if the template doesn't exist