The Google Play Store seems to have fixed a bug that has been going on for a few weeks now, due to which many apps, especially fresh ones for publication, don't appear in search results when the query is the exact name of the app itself. A reporting thread on Google's support forum has over 200 comments from developers whose apps have experienced this issue.
One of the apps involved is Sefine QR: many similar apps appear but not that, although the app is regularly online and available using a direct link. Curiously, if you are looking very similar expressions, as for example Sefine_QR, there is a positive feedback, although it is not always the first at the top as you would expect. Of course, such a bug is a big problem for developers, as research plays a key role in the spread of apps.
Google has not released official information, but for a few hours multiple developers report that the situation is finally back to normal, after about a month.