I am sorry to say that the scenario you described screamed 'potential trouble'! to me when I read it.
A. There is an event that MUST occur
B. A PLAYER's enjoyment is dependend on the outcome
C. The setup is such that there is only a single trigger for the event (the screams and ruckuss)
D. The motivations of the other PCs are not tied in any way the the event (other than: you're adventurers and thus you should want to investigate trouble downstairs)
You were taking a gamble with this setup, and sometimes you just lose such a gamble. It happens to all DMs. Maybe you are blessed with players that often react as you expect them too react, and then its often easy to fall into creating setups such as you did, because 90% of the time they succeed immediately, and most of the other cases you can get the players on track by making a few on-the-fly adjustments. 
If you don't have easy players I would suggest:
1. Preparing several alternate events that fullfill the same purpose:
Tell the other player that he may meet the new PC cleric in town, or on a campsite a day later, or when looking for a potential employer. Just setup different routes to the same event, your players will never know anyway.
2. Metagame
If a player's enjoyment of the game is at stake I always inform the other players. That way they can work with me to bring about the event instead of (inadvertently) against me.
3. Make multiple triggers
Maybe the Sorcerer is asked to pay the bribe to the guard at the inn, and is asked downstairs just before the cleric confronts the dwarf. Maybe the fighter outside sees a gateguard stagger around with a bottle of drink, leaving the gate unguarded when a group of nasty ogres approaches from the east.
4. Tie the event to other PCs motivations
If one of the PCs is looking for a long-lost sibling, have the cleric carry a piece of vital information. If one of the PCs is looking for riches, have the cleric carry a treasure map he wants to sell. That way the other PCs will automatically gravitate towards the event.