@It'sTheTickerTocker posts on danbooru get deleted if nobody approves them. These were uploaded 6 years ago - a lot of approvers have come and gone in the meanwhile so we can't exactly give you a correct response besides "nobody liked it at the time and nobody who liked it and was also an approver saw them since then".
There's also the fact that this is not really a notable CG set (as far as they go), and danbooru tries to be an anime art site before a porn site, so that kind of content (CG sets, purely explicit doujinshi, erotic game rips, etc) often has a hard time getting approved unless it's of decisively above average quality, simply because there's so many sites out there (above all, EHentai) that do the job of archiving this content much better than danbooru could ever do.
The fact that it's a set of sourceless uploads also plays a part in its lack of approval (see help:image source).
This stupid girl, whose photo I've taken while she's definitely shoplifting right there, is Akai Miho from my class. She always makes fun of me, by calling me things like "pig" or "trash".But when I let that Miho take a glance at this photo, her face suddenly paled. (laugh) When I told her to come to my place, so I could give her the photo, she obediently nodded her head.Just imagining how I'm going to pay her back for how she usually made fun of me, makes my pre-cum flow without end. Fuhihi...