If they didn't cite your paper that's bullshit.

But if they read your paper enough that they invited you to a talk, that probably means they were far enough along to independently inventing it they were going to do so anyway, and wanted to chat with someone who was also doing the thing they were already doing. Good ideas tend to reveal themselves to anyone who is aware of the problem.

To be clear, I am not claiming they stole an idea. They have made significant independent research. However, a specific part regarding the treatment of rotation with bias correction relates to prior work, and it would be appropriate to have that recognized.

The earlier paper was from 2021!

Doesn't matter, you should still cite. It's basic manners in science.

> But if they read your paper enough that they invited you to a talk, that probably means they were far enough along to independently inventing it

That's more than a stretch. They likely invented them because someone thought the abstract sounded interesting, or something like that.