If your loyalty program allows guest users to sign up through the app or the iFrame, you can use the Punchh platform to determine which method was used (Mobile App or iFrame). To do so, navigate to the account in question and scroll to the very beginning of the timeline. Look for the 'Joined Us via X' entry. See below:
'Joined Us via MobileEmail' indicates that the guest signed up through the mobile app.
'Joined Us via WebEmail' indicates that the guest signed up through the iFrame.