In the last month I have had to show my FB card twice to get admitted into lounges that admit sky priority but are administered by other parties:
- Madrid (Puerta del Sol at T3, flying KLM)
- Miami (LATAM lounge at J concourse, flying Air France)
My boarding pass with the "sky priority" label wasn't enough, either I was flying business (was not) or needed to show them an elegible card. I'm glad I had my FB card with me but I didn't think carrying the card was needed for lounges (neither do AF/KL because for my first entire year as platinum they didn't even send a card). Madrid had not asked me for the card before so who knows... just sharing this info in case someone is leaving their card at home!