To be fair, I’m freaking out now because I swear there used to be a yellow seahorse emoji.

Someone needs to create one for comedy purposes and start distributing it as a very lightweight small gif with transparency

When I first heard this however I imagined it as brown colored (and not the simpler yellow style)

I learned there really is a mermaid/merman/merperson emoji and now I just want to know why.

For an intuitive explanation see https://news.ycombinator.com/item?id=45487510. For a more precise (but still intuitive) explanation, see my response to that comment.

404 for me, maybe try archive.is?