MAPPED NETWORK DRIVES

I have a friend who has an application that has a wireless network in his
home. The two computers use an application whereby one of the computer
houses the main database. The other computer accesses the data for the
application trough the computer with the main database. To enable this I had
to map a network drive to the other computer and let the application know
that it needs to look for it there.

This friend took the computer out of the wireless range and now that he has
returned within the range everything seems to work well. However, I had to
have him reboot his PC to re-establish the mapped network drive.

1. With the wireless network, is there something within the router that I
need to set up for internal network reconnectivity.
2. Why would the mapped networked drive loose it's connectivity but still be
able to get to the internet.
3. Could he have done this without having to reboot?

Please explain why it didn't re-establsh the mapped drive but it reconnected
into the internet.