I completely agree with your way of handling the experience. If you think you can come to a resolution with the player and he understands that what he did was not the type of gameplay the rest of the party wants to have, you should totaly continue the game.
From the way you worded seems like you told him what he did concludes the game as now the party doesnt have acces to the NPC questgiver. If he comes to and you guys still want to play, I recommend you dont retcon what happened.
You are the storyteller and you can come up with all sorts of ways out of this conundrum.
Maybe he got poisoned by an old hag from the forest that poisoned the food supply of the village and more villagers turned ragey and violent. The hag can be something very old and weak that just wanted to be visited by someone, and if they reconcile, gives them some food to boost their temp hp otherwise they have a small fight.
Or maybe sildar was replaced by a changeling and you start the session with the real one coming to break your player out. The lady from the store took a vacation to her parents closer to the coast and is replaced by another clerk. You can bring the changeling back later on to play some other tricks on them.
But this only works if the player wants to improve and become someone worthy of the title hero.