Borrowed the Neighbor's Lawn Gnome Without Asking

I know it's a silly thing to do, but I really wanted that big purple lawn gnome with stars on its hat. It looked so out of place in my neighbor's sea of green grass that I figured borrowing it wouldn't hurt anyone. So one night, when the moon was full and there wasn't a cloud in sight, I snuck over and brought it home to adorn my own boring patch of lawn. Now it sits proudly among my potted plants like nothing ever happened. Is this kind of harmless fun normal? What should I do if they notice it’s missing? Am I just being petty for enjoying something so trivial? Should I go back with a gift or a note? Let me know what you think!