Q: Was it a case of plagiarism?
It was an event in the 1990s. The data I obtained for my graduation thesis was used by my supervisor in the following year. When verbally asked in advance if it was okay to use it, I agreed. However, my name was not mentioned in the references of the supervisor’s paper.
At that time, was it considered that the college student's bachelor thesis, who was not even a master's student, belonged to a supervisor?
Unfortunately, the answer is YES! When someone presents your work or part of your work—with or without your consent; and most importantly, without acknowledgement, it is termed as plagiarism.
All published and unpublished material, in printed or electronic form, is covered under this definition. So, be it any era, if you have made a substantial contribution to a research—you duly deserve authorship. Sadly, this is quite common in academia when students do not wish to pursue further studies, supervisors conveniently ghost their contribution (search for Ghost authorship: https://publicationethics.org/authorship).
In such cases, the student has to ask for their authorship and supervisor CANNOT deny as it is considered an unethical practice otherwise (http://www.icmje.org/recommendations/browse/roles-and-responsibilities/defining-the-role-of-authors-and-contributors.html)
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