After wondering where the piece of Vettel's endplate got stuck, and how/why it didn't dislodge, but did cost him a lot (I thought maybe under the floor, but that should have produced some sparks, right?), the-race.com had an article about it, giving this picture:
So, why is this relevant for the W11? Well, I think one can nicely see that, here to Bottas detriment, the aerodynamics guided that sailing bit of endplate nicely behind the barge-boards, which is probably where it got stuck from being to big to be guided around the sidepods!