How do I complete quest a with an untriggered event in Elder Scrolls Oblivion?

Solution 1:

According to the UESP entry for this quest,

"For some, you may have to travel all the way back to the Dining Room area before Jakben attacks you."

Have you tried travelling back to the dining area of Jakben's house? For others having this problem who haven't gone and done other quests after the glitch like the OP has, try waiting -- apparently that fixes the issue sometimes as well.

If you've tried all of the above, then you likely need to resort to console commands:

• setstage TG10Boots 45 (Sets your quest objective to be "I have the boots. Now to get back to the Gray Fox in Ganredhel's house in Cheydinhal.")
• player.additem 000148D4 1 (Adds the boots to your inventory, assuming you don't have them).

At this point, I don't think you need the actual diary object, but if you still want it, you can use the following console command : player.additem 000152fc 1