The customer produces a note of their own from a sleeve (napkins? Void forbid they be reduced to that) and responds.
Originally Posted by Note
We will offer [modest amount] in gold or a 20% larger value of potions or other alchemical items. Pick up initial payment at [address in the slums] 1 hour from now.
If you need to contact us, we'll be in your dreams.
When the last stroke is added to the note, they take a slow step back and vanish. Apparently just gone, like Oliver's been writing all alone this whole time, though in fact it's just a trick of the senses, and the customer is lurking at the bar once more.
Oliver reads the note and mouths the words "in your dreams" confusedly. He looks up, ready to ask a question, but sees nothing. He puts away the sign, brows furrowed, and finishes his drink before walking out of the Den to hunt down this address and scope it out.
Linklele made my awesome avatar! Thank you so much!