As Jim Eisenbraun pointed out to you on Twitter, it is normal for publisher not to display the translator on the cover. And, I'd like to point out that K.C. is an editor at W&S, so he might have had some input on that.Sorry if you don't like my comment, but it's the truth. Not dissing translators in any way, shape, or form. They do difficult and necessary work, but if the book doesn't sell, their work will be in vain. And publisher will go away, which some of you may think is a good thing, but when I look at some self-pub stuff, with egregious factual, grammatical, and other obvious errors, I suspect the wild, wild west of self-pubs might not be the utopia that some seem to think it is.
The cover is for selling the book. The title page is where the important stuff is. Worldcat, the librarians tool, usually only displays the translator in the (now hidden) details screen.
The only exception is where the translator is in some way a "big name" and having his/her name on the cover will help sell the book. Because that's what covers are for—to catch people's eyes so that they will buy the book. Period. Actually, exclamation point. Covers are a selling point—which is why the old-style stamped cloth cover is not around much anymore. It's usually on over-priced books that only need to sell 100 copies to libraries to make money. Popular-priced books need a cover to attract the nonlibrarians. If having the translator on the cover helps sell the book, then it will probably appear there. If not, too bad, so sad.
Sorry if I sound cynical, but with the proliferation of illegal sharing sites and people just not buying books, selling the few that a publisher does is what the cover is all about. (And note, too, that libraries are cutting way back on buying books.)
Tell me I'm wrong…