This suggests to me that the buffer has not been saved into your filesystem yet. Try C-c C-c to commit your capture. Automatic update of the cache DB is done when you save the buffer.
You may like to read through some more material to get started with Org-roam. This section of the official user manual has a quick walk-through of the system. I have also started documenting basic elements of Org-roam to complement the official user manual. This chapter on the capturing process might be useful to you.