For those that have a missing crewman like I have, I've just found a solution. You will lose him permanently but at least you'll be able to get a replacement. One thing necessary in oder to to this is have SHIII Commander installed. I'm using version 2.5 so I'm not sure about 2.6, tho I assume it'll still be workable. You must remember his name for it to work or you'll replace the wrong Officer, and also be "In Base".
Before you start SHIII, open SHIII Commander and click on "Click for available actions", then click on "Manage your crew". Seeing he is an Officer, he should be the last officer in the list of 5. Click on his name and it should show "Auto Fix" in the Suggestions box. Click that and "Dismiss" or "Release" him should show. Do either and he is gone. Now continue on to SHIII and start a new patrol. Go into the Crew section then into the available Officers list to choose one for his replacement. Now you can pick a new officer to replace the one that jumped ship and is missing. He'll now be available and ready for active duty.
Now, the most important thing to remember, as we've been told before, never leave him in the Repair section when you close out a patrol, or SHIII when you save in while on patrol. Just to make sure he sticks around.
