Buy player by watching video still costs 1 BC
When buying a player from the transferlist, you can choose between buying by watching a video (+ ingame money), or playing a Boss Coin (+ ingame money). Yesterday, I bought a few players via videos, but it still subtracted BCs.
OSM app updated 25 Feb 2019
This is because info hasn't been updated as at the time player was bought. Usually, boss coins will be added on refresh (when we click on our boss coins) or on next login, most of the times we may not notice it.
But if you're sure that this isn't the case then you have to make a full and complete bug report by filling the bug template that can be found on the "Important Please Read" topic.