When FS#2 first moved in he took his backpack with him EVERYtime we left the house. We could be driving to the end of the driveway to check for the mail, didn't matter, backpack came with him. In the backpack was all the things that were important to him, journal, artwork, stories he had written, cards, anything that he felt made up his identity. Clearly FS#2 suffers from abandoment issues--like no duh! When you never knew if/when your Mom was going to come back to pick you up, you learn to be prepared.
I guess FS#2 has decided that he might be staying here longtime after all.