It's amazing it works at all!
It is possible to copy a keyframe from one PRJ, load a new PRJ and paste the Keyframe onto the same character. Try doing that in any other software!
However, without watching you do it i don't know what filters you have set, nor how fully keyed the bones are keyed in each case. For example, if you copy a key from a bone that has translation keyed but is still unkeyed at it's default rotation, and paste that onto a bone that has translation and rotation keyed, you'll get the new translation but no new rotation.
What you are trying to do is far beyond the scope of "It's a pitch" which is intended as a bare introduction to keyframing.
My suggestion... bite the bullet, pick one PRJ and redo the missing pose and then continue on. Lesson learned and the extra practice posing the character will do you good!
Also, watch my "Keyframing Basics" video, in the tuts link in my signature, for further explanation of keyframing workflow and info about filters.
I hope to cover the topic better in a NewTaoA:M segment, but that's for the future.