Salt Stack environments ignoring saltenv
State and pillar environments are set independently.

Specifing

environment: prod


in the minion configuration will force the minion to use the prod state, but it will still use the default pillar data. To select a pillar environment you will also need:

pillarenv: prod


This also does not work in old versions of salt and is only supported with pillar.get as of salt version 2016.3, so you may be in need of an update.