Help on T situation

[BlueDevilRef]

Ok let me see if I can remember correctly here:

End of first quarter tonight. Black team has a player shooting FT's. He is wearing #8. I did not even recognize this until about five mins later, during 2nd quarter. At this point, nobody has said anything, other coaches or the book. So, I tell the black team coach that if 8 comes back into game, it would be a T. I now realize I screwed this up as if should have had the T as soon as I discovered it. I got it messed up thinking he was okay since he wasn't in the game.

Coach advised us at halftime he was changing the number which he did. So we assessed the T and moved on per 10-1-2c.

I've got that I messed up as noted above. My issue now is the difference between articles b,c,d (penalized when they occur), and E (pen when discovered). I've not read case book yet on this issue but can somebody tell me the difference? For b,c,d, if I am not aware of it when it happens, there is no penalty?