Should I mail my advisor concerning his attitude towards me, and possible re-use of my ideas by a colleague? I have been doing some research for my masterthesis. I had a supervisor for this task, who was (to my opinion) quite harsh and unhelpful in his feedback. I pursued it nevertheless, and continued on the work that I had been doing; but got somewhat annoyed.
Some time ago, he sent me a (edit: yet unpublished) paper by one of his colleagues (with whom he had previously been working with) on a topic that somewhat overlaps with the topic I had been working in. 3 out of the 5 concepts that I used in my paper are also presented in this paper (with a somewhat different name, but the construct on its' own is the same); although the actual question, and other concepts were also added to it - so it's not quite a copy-paste, but I had a sense that this (not yet published paper) was in some ways inspired by my work. The most troubling aspect I found was how my supervisor treated my ideas as 'unoriginal' and also did not give me much support throughout my work while he then send me something that I felt was actually originally coming from me.
I have contacted already a third person about this (edit: an ombuds-person, who is also a professor at my faculty), and am thinking about sending to my supervisor regarding my disappointments and questions about this issue later on, once I finished my exams and obtained my master.
But I don't expect much helpful answers back (I am slightly resentful of that moment, and I am wondering how I can do this at the same time politely and honestly).
I was wondering whether anyone had some similar experience, and could help me figure out what I should do? Should I let it go, later on? Do I also have any say in this?
It is not only my own personal situation that worries me, it's also about all future students who might have him as a supervisor who might go through something like this - which is everything but a nice way to finish a degree.
So if anyone has any experience, I'd love to hear about it.
Update
I send an email to my promotor, in which I somewhat mentioned my problems. He replied to me back that he was sorry that he was not more present to help me, that I should tell something to my advisor and that he will be there to support me if there is any conflict; that definitely something needs to be fixed here and that he is willing to repair the wrongs. So to anyone feeling stuck in a similar situation, I guess my best advice would be: talk about it, and with as many persons as you can - you might not have the answer directly from one person at one moment, but it also just helps figuring what the problem is in the first place. Thanks for everyone having replied in the comments, that was really nice &amp; helpful! :)
I have contacted already a third person about this (edit: an ombuds-person, who is also a professor at my faculty)

This ombudsperson is probably the person best suited to give advice about whether misconduct occurred and what your options may be. Given that you are already talking to an ombudsperson, I would not want to add my own speculation into the mix.

[I] am thinking about sending to my supervisor regarding my disappointments and questions about this issue later on, once I finished my exams and obtained my master.

Your instinct to wait until after finalizing your degree is probably a good one. As for the advisability of writing such a letter at all: well, I am afraid I do not see much point. Certainly it seems unlikely that your advisor will say &quot;Egads! I have seen the error of my ways and am overcome with remorse!&quot; Your desire to protect future students is admirable, but unless the ombudsperson recommends further action, I suspect your options will be somewhat limited.