Concerning the recent "query on authorship," there is no ethical ambiguity. The ESA Code of Ethics is quite clear on that point: "Researchers will not add or delete authors from a manuscript submitted for publication without consent of those authors. Researchers will not include as coauthor(s) any individual who has not agreed to the content of the final version of the manuscript."
If you can't locate the person who contributed, that person can consent to the manuscript. Just note their contribution in the acknowledgements section of the paper.
