With out the thimble rib resting on the bottom of the barrel, are you able to put the thimble rib screws into the barrel?

If the trigger does not fall, check the lock outside the rifle stock. Engage the hammer to the back firing position and then on the botton of the lock you will see the fly and the sear. Watch your fingers, but if you apply pressure to the sear it will trip the sear spring and the hammer should fall. If this works then you might have to check and make sure the triggers are in the right place when you set the lock.

Are you sure you did not get the right screws? If you did not get the screws you need, I would contact Cabela's. They might in turn have you contact Investarms or Lyman Rifles. I am not sure who handles the warranty on those rifles.