But before you do, please at least consider the possibility that you are mistaken. If you can't find a cancel message after a diligent search, chances are there isn't one. Knowledgeable people watch the newsgroup constantly and cancels are usually spotted and dealt with very quickly. If there is no cancel message it is highly likely that no-one has molested your article. Usenet is not a reliable medium.
Articles go missing all the time for a variety of mundane technical reasons.
In the majority of cases the best thing to do is simply to repost the article after 3 or 4 days, with a little note to the effect that you didn't get any response the first time. If you are still convinced something is happening, post your suspicions to the newsgroup, along with any evidence you have come up with. If you prefer not to draw attention to yourself, the FAQ maintainer is always happy to help out.