There would be a break in the Aura. The Aura surrounds the magical effect. There for there would be a gap in the aura the shap of the creature. Hence you know exactly where the creature is.
If this how Wizards is saying Detect magic and Arcane sight work, they should not have used the word aura. They should have changed it to illumination or something else. The pure definition of aura is a "A distinctive but intangible quality that seems to surround a person or thing". If a...
I think that it all depends on what your definition of "aura" is. Detect magic stats that you detect magical aura. The plan definition of aura is "A distinctive but intangible quality that seems to surround a person or thing". That would make me belive that an invisable creature that used magic...