By 12:30 a.m., it was a mob scene at the revamped Marquee nightclub in Chelsea, where Patricia Field and Susanne Bartsch were hosting a Valentine’s Ball with Michael Fragoso (of Le Baron’s Les Garçons). The event was also Ms. Field’s birthday party and rumors flew about it becoming the unofficial Marc Jacobs after-party.

“I think any reason to have a party, you should absolutely party,” Ms. Field said, after blowing out the three candles on her cake ...