How can I track respondents on an anonymous survey?

Can I track users from a pre-event survey into a post-event survey without losing anonymity? I looked at the Unique ID add-on but that only generates an ID for that specific instance. I would like to anonymously track a user across surveys.

To help explain: I am evaluating the effectiveness of social outreach programs. I would like the participants to take a survey before they start the program, then take the same survey after the program concludes. I need to be able compare the pre survey to the post survey without knowing the name of the person who took the survey.

You can check the IP address of the users who submitted the form to find out if they have completed the pre-event and post-event survey. To view the IP address, simply follow the steps below:

1. Go to your form submissions page

2. Click the gear icon on the top right 

3. Check the IP checkbox and click the gear icon again to save the settings.

If you need further assistance, please do let us know.
Regards.