A variety of issues could have caused it -- indexer could have just missed the page. COnsidering the enormous nbumber of pages they have digitized and indexed and coordinated with their search engine & database glitches are sure to occur. I also use Heritage Quest when I am having no luck at all on Ancestry.

One thing you can try, since you have seen the document, is to search for neighbors -- many times a more clearly written neighbors name will be correctly indexed --

sometimes though there are just human errors in the process