Review the conversation between the 2 thugs.
A scroll of teleport never comes with a preprogramed place to Sid's knowledge. Though it may be also possible to divine the writer of the note or to attempt to scry on them, but neither is a 100% certainty The scrying at leat is worth a try, legend lore isn't cheap, though.
well, i dont see the clue u planted, other then i will go for the scroll of teleport, and find out where it ends its destination, or is it a general one? and ingame is there a possibility to divine the writer of a note?