I would say what happens to the tweet itself is almost an afterthought—it was one of only many violations addressed by the report, along with more mundane stuff

I would say what happens to the tweet itself is almost an afterthought—it was one of only many violations addressed by the report, along with more mundane stuff, like contract provisions about employees speaking to the press (ruling: it's unlawful to prevent employees from speaking with the press as long as they make it clear they don't represent the company). The NLRB also required them to post notices addressing the tweet at all factories, and it was immortalized in a 55 page public document—not to mention all of the contemporaneous news reports. I think it's very safe to say that posterity is not going to have a hard time finding this tweet