Suppose someone casts Message while hiding from the target. Would anything be revealed about the caster's location?
Message (Player's Handbook entry) has a verbal component other than the message that is sent, so the target would know as much about the caster's location as they would with any other speech if they heard that part. (A related discussion on whether other characters can hear the message can be found here.)
However, suppose the target did not hear the initial casting of the spell. Would they know where the message came from? I found this question about spells in general not revealing the caster's location in 3.5e, but I'm not sure if it applies to 5e or if Message would be different from other spells.