I have a custom object that looks up to Contact. On the Person Account Detail page, I have a custom button on the related list for this custom object. In production, this button references {!Contact.ID} which pulls the Contact ID of the Person Account.
However, in my Spring '13 sandbox, this no longer seems to work. The merge field is returning a blank value. I tried {!Account.PersonContactID} but this field is not accessible so I cannot save the button. Also {!Account.ID} will not work as I am using this button to populate the Contact lookup on my custom object.
Did something change in Spring 13 that caused this functionality to stop working?