There is not currently a way to export the information that is available in the Audit Log for guests on time of unsubscribe or reason. You can see the Audit Log for a guest by going to the guest account, selecting "Edit Profile" and selecting Audit Log on the top-right.
You can see the Subscription Status as seen below.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)