Has changing the network setting on the mac redirected Bitcoin core to install somewhere else entirely?
Not usually the case, unless it somehow broken the path to your default data directory and bitcoin.conf file where you set the custom datadir while the GUI's setting is set to default.
In that case, it'll create a new "
bitcoin" folder in the default datadir at the correct path and save the blockchain and other data there.
(
the folder may be hidden)
If the custom datadir is set in the GUI's config instead (
set in the Welcome Screen) and the path to "
com.Bitcoin" somehow messed up by the network setting change,
In the next restart of Bitcoin Core, the Welcome screen will prompt you again to set the data directory,
if you didn't noticed and just clicked ok, it'll use the default internal drive.