o2bebowhunting

i was hunting yesterday and had a decent buck closing the distance. i went to pull the hammer back and it would not budge. ive had this happen one other time about 2-3 years ago and i recovered in time. yesterday i did not. the time before i simply opened the gun threw the cap away and put a new one on. i was too late yesterday. when i put a new cap on the hammer came back(after the buck was gone). why did this happen? i dont hunt a lot w/ the TC as you can tell. my gun shot the day before yesterday killing a 7pt without fail. i have 2 or 3 brand names in my possibles bag. it cant be just one of the brands. i even tried(to save time) just taking the existing cap off and putting it back on. that did not work as i had to put a new cap on in order for it to work.

thanks in advance.