As an anonymous user, I gave an answer to this question:
I gave a link to a paper of Zagier which explains how one can write special values of Dedekind zeta functions (for fields with one complex place). The paper gives a clear explanation with references about how this arises by computing the volume of arithmetic hyperbolic manifolds in two ways: one using the volume formula for arithmetic manifolds, where the zeta function comes up, and the other using decompositions into ideal tetrahedra, where the dilogarithm comes up.
The OP responded in comments to my answer in a somewhat antagonistic manner, saying (in part, I don't remember exactly) that he needed a full answer to his question. It's the OP's prerogative to not vote up any answer if they like, of course, although the link in my answer really does explain what is going on (and even makes it clear how to do the explicit details if you really wanted to). But I generally find it best not to persist in these situations so I left a dismissive comment that began with "lol" and explained that I had no intention interacting any further with the OP. Even though I intended never to revisit the question again, I happened to see it in the question list as having "no answers" even though I had given one.
I can't tell what happened, and maybe I am mistaken, but it seems as though a high reputation user in a fit of pique deleted a perfectly good answer to a question. Maybe something else happened (the OP deleted the original question and asked it again, maybe? the effect is the same), but if my speculation is correct, that seems extremely contrary to the purported aims of this website.
Update: If the answer to a question is: "there is a standard technique in the field for showing why this is true, here is a paper which explains in detail the general principle" then what exactly is appropriate for an answer? A book length treatise on hyperbolic geometry?
To be clear, the answer was not just a link only answer, but it had a few sentences of discussion as well as precise reference to the particular paper which discusses the very essence of the question. I did indeed "summarize the content of the link." namely, the equality follows because you compute the volume in two different ways. Would it be better just to replace the link to the paper with the name of the paper and give the same answer? Someone could easily have edited it to this effect.
I genuinely think that it was a useful answer to the question to anyone who was willing and able to engage with the material. Moreover any full answer to this question requires a certain amount of sophistication and engagement with the material that I directly linked to. The fact that an undergraduate OP doesn't have that sophistication is not surprising, but answers are (supposedly) also supposed to be for other people who visit the site.
Update Update: Thanks for the explanation of the underlying process. The answer seems to have been (at least temporarily) resuscitated, so people can see for themselves if it is truly a "link-only" answer. The problem in this case seems to be that there is a gulf between the understanding of the OP and the answer. There's really no easy way to resolve this (Paramanand Singh in the comments suggests I could write five pages of explanation). But if it is the policy of the site to delete such answers, then I accept that.