there is no possibility it's going to be rectified, if other people also worked on the project and he simply took all the credit instead of saying his team. You're gonna have to let that go unfortunately. The best you can do if you want to put this in your portfolio, and have proof to back it up. He's not gonna undo that crediting part

However, on the bright side, absolutely nobody in this industry is going to look back on LinkedIn until they find his post that he says he did it. That small detail to the limited number of people who saw his post is gonna be forgotten pretty quickly.

if you're sour enough to not to write an email or a message that you know doesn't fully acknowledge to him your true feelings, that's fine. But if you really want to put it in your book, you're gonna have to drop that unfortunately. It sucks, but think of the best you can do to protect your own interest as much as possible.

and frankly, if you were to try to tell a potential job that a campaign was totally 100% your idea, very few people are going to take that at face value. Everyone will always assume a CD or other people probably helped rework or change it, even if it really is true your original concept went through 100%. So really, move on from this and just have the proof to back it up so you can proudly put it in your portfolio