There's a bit of a weird myth with robots.txt and the idea that it prevents pages from showing up in search engine indexes. Robots.txt means that the search engine cannot crawl the page - it can still include it in the search results if it sees enough sites linking to it. It can take a guess at what the page title can be, but there's usually no descriptive snippet because it's unable to see what's on the page.

If you don't want the page to be included in the index at all, you can use the meta noindex tag, by putting this in the head:

<meta name="robots" content="noindex" />

Pro tip: you need to also unblock that page from robots.txt - if Google isn't allowed to crawl the page, it can't see the meta noindex tag, which means it would stay indexed.