When you download the survey responses it will give you the responses to particular questions defined in your action alert (like a survey), but questions are not required so if you don't ask any questions you won't get any responses. For more information on why this report doesn't always provide the expected results, see this article.

To see who has sent the action alert:
  1. Create a query
  2. In Query Builder, click on "add an interaction clause"
  3. For Interaction Group choose "Referenced Types"
  4. For Interaction Type choose "Action Alert Response"
  5. Choose the particular action alert and run the query
OR
  1. Go to "Data Management" > "Reports"
  2. Expand the "Advocacy Reports" folder
  3. Click on the "Alert Respondent"
  4. Follow the on screen prompts to generate a report