Which act is NOT considered theft under California Penal Code?

The act defined in the question as taking an item valued at $1000 with intent to return it is not considered theft under California Penal Code due to the principle of intent. In California law, theft requires the unlawful taking of someone else's property with the intent to permanently deprive the owner of it. If an individual takes property with the intention of returning it, this does not meet the legal definition of theft, as there is no intent to permanently deprive the owner of their property.

In contrast, the other scenarios involve actions that are classified as theft because they demonstrate an intent to take and keep someone else's property unlawfully. Taking a bicycle valued at $800 represents theft, as it indicates a permanent deprivation. Borrowing a friend's item without permission also qualifies as theft since it involves taking someone else’s property without consent. Shoplifting an item worth $300 is considered theft, as it involves taking goods from a store without paying for them. Hence, the intent to return the item makes that specific act distinct from the other examples that clearly fit into the category of theft.