I've read a few sources on ARP and Mobile IP and I couldn't find the answer to this question (or the answer simply escapes me). I'll write a short summary as to what I've learned about this topic.
So, a host sends IP packets to a host on its network using the link layer (MAC) address of that host. With mobile ip, the home agent impersonates the mobile node by broadcasting gratuitous and proxy ARP messages in the home network of the mobile node (the hosts on the network will update their ARP cache and associate the IP address of the mobile node with the MAC address of the home agent). This solves the problem of hosts on the mobile node's home network sending IP packets to the mobile node (the home agent intercepts the packets and tunnels them to the care-of address of the mobile node).
Now, I ask myself, how does the mobile node send IP packets to hosts on its home network? From what I've read so far, the mobile node sends IP traffic according to normal IP routing. This implies that, for hosts on its network, the mobile node will try to send them the packets directly using the MAC address (will not forward the packets to a gateway). What am I missing here? Is traffic destined for the home network hosts forwarded to the foreign agent directly? Can you point me to some references? I didn't find any answer in tcpipguide.