I have seen "joined from desertion" before. When a man went AWOL for some time, his status was eventually changed to deserter. If the man came back it was called "joined from desertion" or "returned from desertion". Usually there was some punishment including loss of pay (but he wasn't shot). Usually it was brig time or extra duty and in some cases loss of a stripe, but the latter was not possible for a private of course.

My personal opinion is that they declared soldiers AWOL to quick a lot of times. It just meant they didn't know where he was. My gg grandfather Charles P. Dickerson was declared AWOL when actually he was a prisoner of war.

Fred