This is really odd and I only noticed it when trying to reproduce https://forum.matomo.org/t/matomo-help-buttons/33205

Steps to reproduce:

• Open
  https://demo.matomo.org/index.php?module=CoreHome&action=index&idSite=62&period=day&date=yesterday#?idSite=62&period=day&date=yesterday&category=General_Visitors&subcategory=General_Overview
• Hover over "Visits Over Time"
• you should see a (?) help icon
  
• go to "Visits Log" in the sidebar
• go back to "Overview"
• hover again over "Visits Over Time"
• there is no more (?) icon
  
• reload the website -> everything is back as before

Bonus Bug:

It seems like when there is no data in the report the help icon also doesn't show up