Right mate we are getting our wires crossed here
Here is how it works. For this exercise we are going to use 4 locos we will call them 201,071,141,121
You are running 121 in recall 1. 201 in recall 2. So you decide you want to run 071 so you enter that locos address now you have 3 locos running 121,201,071.
So you go to look at recall 1 which had 121 in it. It has now dropped 121 and it says 071 but 121 is still running but you only have control over 071. Recall 2 still says 201
So lets call up 141 now you have recall 1 with control over 071 and recall 2 with control over 141. 201 has been dropped from recall 2 but it is still running.
Now we are going to call up 121 again as soon as you do this 121 which was running with no control over it will stop. Recall 1 will now read 121 but 071 will still keep running you now have control over 121 in recall 1
So we now have 201,071 running but not showing in any recall and no control over them and 121 in recall 1 and 141 in recall 2.