Creating clues for an investigation

[ZeroSpace9000]

I'm currently working on a campaign that I'm committing to paper, and I need help making a few more clues for a minor mystery moment. The players are going to be investigating the disappearance of a House Cannith magewright (ie mage-smith) who fled his home/compound for reasons. Said reasons are currently undefined, I will see about putting that up if I can. Anyway, he's run away to Sharn to meet with some kind of trafficker, maybe House Thuranni/Phiarlan, to deliver him to my 'act one' BBEG.

So far, I've got a book of plays, like Macbeth, with a bookmark set for a play being performed in Sharn, and a receipt for a coach ticket to Sharn. I'd like about 5 good clues in total, ideally such that any 3 should give them enough of a lead to proceed. Feedback/critique on the clues I've already got would also be appreciated.

[Grand Poobah]

A NPC friend/colleague/servant of the magewright saw him looking at a map of Sharn, heard him asking about transport to Sharn, saw him boarding the coach to Sharn. Link the NPC to the magewright with a letter or receipt or something noting the two saw each other just prior to his disappearance. Potentially a red herring if the note was somehow threatening "You owe me money!".

Have the PCs find a letter (perhaps coded) from someone in Sharn without specifically mentioning Sharn itself. Maybe a description of some sort of landmark which just so happens to be depicted in a painting in the magewright's house. Trouble is the painting doesn't name a location but the landmark’s surrounding area significant/distinctive enough to be shown on a map so off they go to the local cartographer's guild. E.g “Meet me at the house on the cliffs where we grew up”. Painting shows a house on a cliff but the cliffs look like the profile of a man or the cliffs break off into pillars or teeth. A city can be seen in the background.

A distinctive article of clothing with a pocket, inside of which is a distinctive flower/plant that is only found growing in Sharn. Perhaps there’s a letter with the flower – if the flower is poisonous it could be a threatening letter, if fragrant it could be a love letter depending on why the magewright disappeared.

Several items around the house are of exceptional quality and all of a similar look or style. They all have a carpenter’s mark and name. Off to the local carpenter’s guild which points to Sharn.

[Segev]

I don't know Eberron well enough to be more specific, but if he's meeting with some kind of trafficker, make the trafficker be in something that Sharn is known for, and have a note or a rumor that he was looking for whatever it is he's meeting the trafficker to obtain.