What should I do if I think that my former supervisor has published our results without citation or acknowledgment?
People's work on a publication is attributed in two main ways: authorship and in the acknowledgement section. Here, you need to know if your contribution was significant enough for an authorship (it sounds like it wasn't), and whether your work actually appeared in these publications.  There are a number of resources and guides regarding authorship: one, for example here. The typical defining factor is making an intellectual contribution. The information you have provided suggests that you do not deserve an authorship, but probably should have been noted in the acknowledgements. 

In my opinion, this is not worth making a fuss over. In my experience, admission committees are unlikely to care about whether you appeared in this section or not. They care whether you were an author on a paper, and how your reference letters discuss you and your work. You will have the latter, as long you don't burn any bridges. In your discussions with potential advisors, demonstrate an understanding of why the project was important, and detail how you assisted the main researchers.

Citing your project write-up is unlikely to be appropriate - and plagiarism would probably only come into play if they copied and pasted your text without your permission.