Scrap this if the Advocate is not in play.
The Advocate may choose 1 Guild card held by a Rival, but its suit cannot match any Guild card held by the Advocate.
That Rival must either give that Guild card to the Advocate and take 1 Favor from the Advocate, or give 1 Favor to the Advocate.
This is not stealing, so cards like Sworn Guardians don't prevent it. The Advocate can even demand protected Guild cards!
Act: 2
A: The holder simply gives you a Favor, since they cannot actually give you the card. Sucks for them.