12-12-2016, 02:23 AM
A little further thought and another reading of your post, I'm going to modify my answer somewhat and say that if the source is visible, the caster knows the source, but range is not determinable. As your player pointed out, the spell description does use the word "discovers," but what is discovered? An evil object? No. The spell caster discovers "emanations."
"Yep, that bracelet is emanating evil, as is that vial. Oh, and something on the other side of the door."
"How far away are they?"
"Well, the bracelet is on your wrist, the vial is on that table about ten feet away, and the other thing is somewhere on the other side of the door."
"Can't you tell how far on the other side of the door?"
"What? This is evil we're talking about here. It's not like it obeys the inverse-square law."
"What's the inverse-square law?"
"Exactly."
"Yep, that bracelet is emanating evil, as is that vial. Oh, and something on the other side of the door."
"How far away are they?"
"Well, the bracelet is on your wrist, the vial is on that table about ten feet away, and the other thing is somewhere on the other side of the door."
"Can't you tell how far on the other side of the door?"
"What? This is evil we're talking about here. It's not like it obeys the inverse-square law."
"What's the inverse-square law?"
"Exactly."
Getting me free admission into gaming conventions for a decade