Well youtube rates your videos on watch time and retention as well I believe. If you are targeting a search that returns millions of results, it's very unlikely that your video would be near the top. That doesn't mean your video isn't there, and also it doesn't mean people won't find it. Youtube also keeps track of your watch history, watch patterns, etc, so different people from different locations will likely see different results when they search the same keywords.
For instance, I noticed that every time I upload a new video, I get an influx of views on it for about 2 days. I usually get around 30-80 views on new videos within the first 2 days. It may not seem like much, but for a small channel like mine, it's quite a bit. After those 2 days, things die down a bit. When I check the traffic sources, the biggest source is search results, and the top 2 keywords are are always "fart" and "farting." When I try searching for my video with those terms, I can't find it. Somehow people are able to find my videos through search by just typing in "fart", so I think either they go to like the 12 page of results, or it has to do with watch patterns.
