Provided a PC has access to the School of Divination aspect then it makes sense that they might create an advantage using their spell-casting profession to uncover magical aspects in a scene. Those aspects may describe the lingering effects of spells, the presence of prohibitive magic in the form of wards or even the state of the weave itself when wild magics run unchecked.
In situations as described above a create an advantage action will be called for with passive opposition providing the difficulty. If the aspect being uncovered is particularly unique, then the Dungeon Master might be applying the Bronze Rule and treating the magic as being akin to a character, with multiple aspects and stunts. This makes a lot of sense in the case of high-level wards – prohibitive magics programmed to respond in specific ways to trespassers. In Faerûn every mage worth knowing employs a sigil as a kind of occult signature. If used for warding purposes that sigil may be reinforced by a number of charged glyphs, each one working in concert to contribute to a powerful ward.
Of course if the Player Character has access to the Detect Magic spell as described in the Freeport Companion then there may be no need to go to the dice but even if a magical aspect is revealed it’s effect may continue to influence and affect the scene: just like any other game or situation aspect. How to remove that aspect will be decided between players and Dungeon Master.
For some inspired ideas describing magical wards and traps see this page over at the Alexandrian blog: http://thealexandrian.net/wordpress/12909/roleplaying-games/thought-of-the-day-disarming-magical-traps