I worked at a university the UK, at the end of 2010s and left on good terms with the research group. Thought boss was a nice guy and was appreciative of being able to use him as a referee. Just yesterday I happened to come across an article published 8 years ago with his, his boss’ and other researchers’ names on, which is mainly on the work I conducted over the 2 years I’ve worked for him. He gave authorship to students who contributed to a minority of the results in the paper, but completely missed me out. Some of the work done by someone else was on bacterial mutants I produced. That was 2 years of my life including many weekends and evenings. I can’t believe he did this to me. The paper reads like he copied my lab book. I always thought it was a shame the work never got published and had to explain to some interviewers for jobs why. All the time my boss and his group were taking credit for 2 years of my work. I might have missed out on jobs or a PhD position because I had nothing to show for the work I did there, and I still don’t as I can’t be referenced for my own research and can’t state the article is of my experiments. I have contacted my previous boss, now working elsewhere. I don’t hold up hope he’ll respond, let alone admit it’s my work. Unfortunately I had to leave my lab books at the university when my contract finished. I have contacted them to ask if I can come in to photograph the pages. No one had a clue and kept passing me on. I don’t hold out hope that they’ll let me see my lab books. Anyone had experience of this or have any advice please?
Since you are alleging serious academic misconduct, you should contact: (1) the person who is responsible -- you already did this and do not expect an answer, but you need give your boss time to respond, and then (2) the institution where both of you worked -- this would also give them an incentive to secure your lab books (3) the outlet where the paper was published (4) the institution where the alleged offender works now, if it is an academic institution.
Normal academic standard is that the university assesses your claim first based on believability and then starts an investigation. Presumably, they do not have a bias against you, but these investigations can take a long time. Be careful to not overstate your case as any untruth can backfire against you. Be also careful about public statements without advice from someone who knows UK libel law.
The first thing is to contact the lead author but do not expect much. Expect even less if you think there will be noticeable consequences to the PI. (This is just a historical fact, not a statement on the validity of the claim.)
You need to be absolutely sure of your facts and timelines, and this will be difficult as you no longer have your lab book. It is easy to claim someone else collected new data (even possibly on a better instrument) and you have limited ways of refuting this claim; in case of any hint of a doubt, expect the institution to rule in favour of the PI. Moreover, collecting data may not be enough (depending on the data) to warrant co-authorship (historical cases of such situations are known).
If possible, keep all the correspondence (email or otherwise) between all parties involved in this case. If anything, it will demonstrate initial good will on your part to resolve the issue amicably. However, plagiarism is very difficult to prove so the most likely outcome is that nothing will change.
You write that you "always thought it was a shame the work never got published", yet you don't describe yourself as having taken any steps to try to get it published. No conversations with the rest of the team about the value of the work. No suggestion that you would write up a draft yourself. And now, you discover that it was published but without your name. Is it unfair? Yes, probably. What should you do?
My advice would be ... move on.
Consider for a moment your chances of doing either of the following:
Making life uncomfortable for the authors on the list. Chance: very very small. Why? Because as university employees, they will be able to shuffle a lot of the heartache of any accusation that you make off onto in-house lawyers.
Having your name appear on the paper? Chance: Zero. Why? Because the chance of having the journal recognize your claim to authorship is very small, and even if it were recognized, your name will be added as an "also ran" in an online correction. Sure, you might belatedly be able to claim some kudos from the citations, but that itself is conditional on the preceding probabilities.
Life is short; too short to waste. And I predict that you will find it even shorter and more wasted if you spend your time nurturing your resentment over having missed authorship on a single publication, no matter much time you worked in a lab on it (8 years ago).