1. An attorney can: a) be expected to hold in confidence any communication where legal advice is given even if it is mere cocktail party chat; and b) be held professionally liable for such communication. A formal retainer agreement is not required to form that relationship.
2. If it was mere cocktail party chat or something inconsequential as is being claimed by Hannity, why would Cohen have discoverable records about the advice given? It is believable that no body wanted the link made public even if there was no shady situation. Maybe there was a pay off for SH but we do not know that.
3. Hannity should have disclosed his conflict before commenting on the impropriety of the raid. But I highly doubt his bosses or audience cares.