Pages that are excluded by robots.txt can appear as URL-only results in the SERPs.
Pages that carry the "noindex" robots meta should not appear in the SERPs as URL only or anything else.
But, since the robots.txt directive is the first thing that a bot sees it does not retrieve the page, so does not see the "noindex" robots meta.
You have to remove the block in the robots.txt so the bot can see the "noindex".
Note that Googlebot works the same way, not sure about Y!.