Your database probably still has them. Look in your phpbb_themes and phpbb_themes_name tables to see if there are any entries other than 1 for theme_id. If so, delete those rows (from both tables). Then, make sure you have only subSilver listed in your /templates directory.
P.S. Also, go into your ACP -> General Admin -> Configuration, make sure that Default Style is set to subSilver, and Override User Style is set to "Yes".