>>7488189It isn't tagged with a hashtag, it's sometimes posted with no words to search for, or some code/abbreviation, or it's under a popiku/privatter that requires a password/for you to be following them/put on a list, or it's posted on a locked account. And like anon said some are so anal they delete their art if it gets too many likes.
Personally, I browse the main hashtags, then stalk the likes section of liver/ship dedicated accounts and usually I find something. I know some have lewd hashtags but some of the best stuff is untagged. It's easiest to put artists who favorite a lot of ship art in a Twitter list so I can return to their likes whenever I feel like looking.
I haven't bothered with Pixiv in about a year now.
