>I was wondering why the listing was removed?
There are basically two possibilities: (1) lack of adequate unique content in this the second internet millenium (the 99% bet), (2) editor error (1% or so chance.) We don't discuss specifics beyond that.
Aside: It is possible that someone will look at the site as a result of this posting (and fix any error they find), but there is of course no such obligation, and we do tell people most emphatically that they must not and may not use this forum to request site reviews.
>If the listing will not be put back into this category will I have to wait another 3 years before the site is submitted...
This sentence doesn't parse, or at least, the verbs and subjects don't seem to fit together in an ODP conversation. "Submittal" is something you as a surfer would do (or not do); and submittal would be the way to suggest adding a site. You are under no obligation to submit any site, or to submit it in any particular time frame.
If you submit a site, then we don't know how long it would be before an editor reviews it -- could be more than three years, could be less than three minutes. The editors have the same freedom you do, to choose when to work in the 'net, and when to do something else. (So nobody can know until afterwards, when anyone will do anything.)
>what category would you recommend that I submit the site to.
There is no need for such a recommendation here. You can submit it anywhere. The closer to a good fit you find, the more it will help us (and possibly, the quicker we'll be likely to review it.) But even if you submit a good site to a wildly inappropriate category, the editors will hunt up the right place for it.
The question you do not ask is "should you resubmit?" The answer is, of course, 99% of the time, a resounding NO, both in moral and practical terms.
But if you are sure that the site has significant content not present on any other site on the web, that it represents the best main entry point of the sole online repository of the sum of your knowledge and experience, (that is, that it is a listable site) AND that it hasn't been abusively submitted already (that is, that no other sites with part of its content or part of your knowledge could possibly have been submitted, and that it hasn't been submitted multiple times to multiple categories already, so that its removal is not related to fraternal mirror or doorway spam or vanity-domain spam or just submittal spam or any other kind of spam) THEN, only if ALL those conditions are met, it would make sense to resubmit the site.
It doesn't make sense to compare your site to listed sites. After all, we might have made multiple mistakes, and the other mistakes not been caught. But if you looked at 99 other REJECTED OR REMOVED sites, and yours wasn't clearly the best of the lot, then you're wasting your time and building frustration for yourself by submitting. But if yours clearly was the best (not at all in site design, not in attractiveness, but in information and content!) then it would make sense to resubmit.
Obviously, this answer is as general as I can make it, because it is such a common question.
Obviously, not all of it may apply to you -- most of it I haven't checked. It's for anyone who's had a site deleted and would like to get some idea of the reasons and the possibilities for re-inclusion.
And ... this is not the place to post your analysis of the site by these guidelines. The reviewing editor probably wouldn't have read, and certainly shouldn't trust, a secondhand review -- we're supposed to be looking at the website and it alone for its unique content (and at other websites for its non-unique content), and we're responsible for the results.