Good afternoon!
I need to receive an opinion on authorship rights. I don't know what kind of action I would like to take, therefore I would like to hear the previous experiences of people who have gone through something similar.
I am a scientist currently working in the Netherlands, but I grew up and studied in Italy.
Almost two years ago, straight after I graduated, I joined a research team for 6 months. They needed someone who would be able to run a few lab tests, take care of the development of two similar projects, and basically be there for six months. The contract could be prolonged for an extra six months, but then it would stop.
I accepted the job, even though it was slightly out of my field, and it went nicely. I did a few tests in the lab, helped a PhD students in running experiments and did a lot of data analysis for the project. The results I helped collecting were used to prepare posters and presentations for conferences and both my bosses and the team members were happy with my performance. We also had dinners and coffee breaks together quite often.
One of my bosses then asked me to stay for the extra six months and maybe to start a PhD project with him in the future. I was very honest with him and admitted that I wanted to move to the Netherlands and start a PhD here, and to move back to my field of study. My boss seemed a bit sad but accepted it.
When the contract finished I moved to the NL, where I work now.
I recently found out that they published a paper and did not mention my name, neither in the author list nor in the acknowledgments. I was not informed they published. My work is there, and so are my data. Half of the paper includes data I contributed in collecting and analyzing. I think I should be mentioned.
What is your opinion about this?
Is there any action I can take?
Thanks in advance!
G.

I don't think there's anything you can do now. It's always a good idea to agree contributions before doing the work. Often 'technicians' (if that's what you were or how they saw you) are only mentioned in acknowledgements.