This was the way I saw deserters handled during my time (1970-1991) in the Coast Guard. When a military member decides to go UA, there are a variety of administrative procedures that the command must take at certain time increments. My memory recalls that after being gone 24 hours, the member goes into a bad time status. That means, he doesn’t draw pay and he owes that time gone to military.
On the tenth day of being UA, An Absentee Wanted by the Armed Forces form is generated and is sent out to literally everyone. Also on the tenth day the member’s locker is broken into and everything is inventoried and is given to the Master at Arms for safekeeping.
On the 30th day, the member is declared a deserter from the military and his personal effects and records are transferred to to the appropriate Coast Guard District Office. If/when the member shows up or is apprehended, the District Office transfers the records and personal effects back to the parent unit.
In most cases, the member is not accused of desertion, because a successful argument was made by saying he was coming back and he still had his ID card on him. So, you do charge him with being UA, missing movement, disobeying a regulation and then look up Article 134 to think of any other charge and specification you can throw at him.
In Bergdahl’s case, he did leave a note, which depending on what it said, could lead the convening authority to try him for desertion.
Personally, based on what I’ve sent the members of his unit say about him, I’ve rather we kept the five psychopaths in GTMO and let that treasonous bastard stay with his new playmates in Afghanistan.