Trulia must be going by zip code because the zip code there is 91301, which is Agoura Hills. If you check it out on google maps (type in the address), it shows as being in Calabasas.
Lots of gated communities in "Calabasas" have some homes as Agoura Hills as their address, whereas the neighbor's address is Agoura Hills.
Kind of weird, but it's the way it is. :)