What should I do when a paper is published similar to my PhD thesis without citation?
Well, if you did not publish, and your thesis is not available, you really can't complain that somebody else's similar independently performed work is not novel - they had no reasonable way of knowing about your work.

Really, the only way to approach it is the first way. And learn that undocumented work buried in a drawer somewhere does not exist as far as the rest of humanity is concerned. Going forward, document and publish (as appropriate) your work (document for internal business use, publish for the outside world).