This just sounds like lazy cops that did not wish to check all the items back into evidence after itemizing and tagging everything. I suggest this as I am also lazy.
One of my housemate's car was stolen and used in a bank robbery and when they recovered it there was a screwdriver in the ignition lock and there were a bunch of cigarettes and music CDs in it that belonged to the thieves. It's possible forensics for a property crime do not matter much to most police departments unless it's a much higher dollar amount involved or murder/assault.
