Tonight during our play session, we ran into an incident where a character immediately used a bardic inspiration after getting it (on their turn, but like it was the first thing they did). The bard's player was curious if he could give the character inspiration again on his turn. He was curious if the bard would know if/when someone actually uses the inspiration bonus.
During the game, we quickly decided "Yes, because it's magic and you are connected to that magic." But I was curious and looked up the info on Bardic Inspiration on page 53 of the PHB:
You can inspire others through stirring words or music. To do so, you use a bonus action on your turn to choose one creature other than yourself within 60 feet of you who can hear you. That creature gains one Bardic Inspiration die, a d6.
Once within the next 10 minutes, the creature can roll the die and add the number rolled to one ability check, attack roll, or saving throw it makes. The creature can wait until after it rolls the d20 before deciding to use the Bardic Inspiration die, but must decide before the DM says whether the roll succeeds or fails. Once the Bardic Inspiration die is rolled, it is lost. A creature can have only one Bardic Inspiration die at a time.
Nothing in that description says that the effect is "magical". Granted, I think it probably is magical and that we guessed correctly, but I am still wondering if there is an official ruling on this.
Does a bard know when a character uses their Bardic Inspiration?