99% sure the coin is just damaged. Imagine the T being there and it getting hit. And in a way that metal moves to form the shape of a Y. Understand, that your coin is most likely damaged in such a way that the T is there. So it is nothing more that a hit, or damage from outside the mint.
@Chuckdcrane The letter T took a hit.. Here is a thread I created on the subject - https://www.cointalk.com/threads/the-liberyy-cent-enigma.309022/ There is no reason for the US Mint to replace T in LIBERTY.