There is no “I attempted to return it therefore it is now mine” exception carved into our common law, nor is there a “I have no admission from the owner that a crime has been committed, therefore I cannot be investigated by the State” affirmative defense.
california law requires an attempt to return it.
that part was done.
THEN the owner has three years to claim it.
that part was done.
the item was returned.
What is the crime? refusal to return? the item was not stolen because there was a verifiable attempt to return and immediate return upon demand.