Where is vim after pkg install?

Ok, that is weird.

On the RPi, pkg install vim goes through the process of downloading 46 packages, but only installs 17 of them. Consequently vim-7.4.1832.txz is never actually installed.

Clearly, this is a bug with one or more of the packages on the ARM platform.

Hopefully, you can live with vim-lite for now.

I guess you are using the default FreeBSD shell: csh ?

This is not bash. You need to update your shell current command dictionary with a simple rehash before trying to access just installed commands.