Not sure if i can keep playing

i really screwed myself over. I just started playing and i was really enjoying one of the free started decks. I played all the way to silver before i decided i wanted to “claim” it before in case i forgot before the timer ran out. Well i clicked “claim” and didnt realize but it pulls up another menu on the side and selects a different deck. I didnt notice i had to reselect the deck i wanted, so i clicked through and accidentally unlocked the wrong deck. I am completely bummed. i dont want this other deck at all and i dont know how to get the cards to play the first deck i was playing. i realize its probably impossible to revert my accident. but im not even sure to how to get the cards i need to build the other deck i liked…