> Are there any situations where you wouldn't be able to find bash in /bin/bash? Yes there are. OpenBSD for instance installs third party software under /usr/

> Are there any situations where you wouldn't be able to find bash in /bin/bash? Yes there are. OpenBSD for instance installs third party software under /usr/local. Bash is not a part of the base system. env(1) on the other hand is a POSIX standard utility and comes with the OS.