What would be the correct word for an instance of an author taking from a primary source, which the author clearly marks as a quotation, which should be given an exact reference to allow the reader to chase up the source, but is not.
‘Plagiarism’ is wrong since the author is not claiming it to be their own work, but it’s a similar sort of failure.
I'm not totally sure what you have in mind. If it's something like:
Original Author says "blah blah."
where the name of the source or the page number should be given, I think Seth Kaplan's suggestion of calling it an "imprecise citation" is appropriate. The original author is given appropriate credit, but it's not as easy as it should be to track down the original source. (How easy it should be varies, though—I assume AP doesn't require page numbers, because I can't remember a journalist ever providing them.)
I do not think there is a single word that would specifically captures this. You could say it was "miscited," but that often suggests the wrong person or source was cited.
If it's something like:
It could be defined as "blah blah."
where the original author is not mentioned at all, I would describe that as an "uncited quotation," or as "failing to give credit."
Also—I would not consider either of these a "similar sort of failure" as plagiarism. Plagiarism is taken so seriously because it is dishonest and a form of cheating. These mistakes are not.
That would be "without attribution," or "lacking a source," or "citation needed" (the latter if editing or reviewing the author's work prior to publication).
It depends on which style guide--Chicago, AP, etc.--you are using. They govern what format citations should take. Varying from that "standard" would probably bring opprobrium that could be termed "imprecise" sourcing.
It is an oversight, as defined by Merriam-Webster
an inadvertent omission or error
That's the polite word. A less polite word would be sloppiness, The Free Dictionary
Showing or in the habit of using little care or attention: sloppy use of language; a sloppy researcher
Which word is appropriate in a given case depends on how many oversights or other errors occurred in the paper; an isolated omission is an oversight, a pattern of omissions and other errors is sloppiness.
