Why is a removed thread still being advertised on Facebook?

[IlikebigboatsandIcannotlie]

Just saw a thread being promoted by Mumsnet on Facebook advertising some weird diet thing.
Clicked on the link as I was shocked the thread was being promoted and it has rightfully been taken down.
So why is it still being advertised on Facebook?

You've basically given this dodgy company a bunch of free advertising!

Hello @IlikebigboatsandIcannotlie thanks for alerting us. We do have filters in place to prevent threads like this being shared but obviously it didn't work here. We'll remove the thread from Facebook now.

Thanks!

(happy for you to remove this thread too as it has the advert in it)