I think Facebook has no ICO because there are several organizations that has come together to finance the project. it is governed by the independent Libra Association tasked with evolving the ecosystem. Members of the Libra Association consist of geographically distributed and diverse businesses, nonprofit and multilateral organizations, and academic institutions. Founding members include Mastercard, PayPal, Stripe, Visa, eBay, Facebook, Lyft, Uber, Spotify etc.