Full stop, right here. The player has stated an action with a goal and approach, the GM is now obligated to narrate the results of that action. If the GM decides there's no uncertainty, the GM still must narrate the outcome.
You continue to imagine the game stops because dice aren't rolled, which is wrong.
No, everything above would never happen because the GM either calls for a check and narrates the outcome or just narrates the outcome if it's certain.
Firstly, this situation wouldn't ever happen in my game because, as presented, it apoears as a social challenge so it would be in my game, but this example isn't. I don't have long question and answer periods with ambulatory exposition.
However, assuming it did, and the clerk isn't lying and there's no consequence for failure ("no answer" isn't a consequence), then I'd narrate that close attention during the exchange reveals the clerk is earnestly trying to help. If the clerk is lying, and I think the approach shoukd autofail (which I do not, I'd ask for a check in this situation with a consequence appropriate to the approach) I'd narrate that there's no indications in the clerk's body language that indicates falsehood.
Regardless, the argument you imagined would never, ever, happen.
Cool, what happens on a failure when the ckerk isn't lying? If the clerk is lying? I, and ithers, have brought this up numerous times that there's a big difference in style on failure, but you keep only presenting success. What does failure look like in your game for this example?
"Cool, what happens on a failure when the ckerk isn't lying? If the clerk is lying? I, and ithers, have brought this up numerous times that there's a big difference in style on failure, but you keep only presenting success. What does failure look like in your game for this example?"
In my game, one of two things happen on a failure to use insight to suss out a lie on a truthful speaker.
1 Failure - no progress - status quo - "As you gauge his responses, its unclear, no clear compelling signs of deception or honesty really shine through to change your mind or confirm your suspicions."
Seems easy right? Not getting to success meant you hot nothing to change your mind.
2 Failure - some progress with setback. "Ok, so, it's a mixed bag but it's pretty clear he is being truthful about some but and not about others. The way he reacts and talks and manners make it look like he is serious about being here that night, likely not being completely truthful about the traps being set and likely not giving you the whole story.
Also seems easy, right? Pick some of the account as ringing true, some not and leave further doubt sown as a way of giving some progress with setback.
In addition, it sets up a less binary scenario result. Is he lying about setting the traps or is he just wondering if he is remembering right? Is it doubt or outright deception? Or, is he being truthful to the questions asked, but there are other questions that need to be asked? Is the truth what he has said, plus the fact he had a lover over before that who he is keeping hidden?
But, to be fair, in my game, I work the quality of the die into the narration too, so if those were a natural 3 failure, I am likely to add more uncertainty into the mix (thus more likely no info narration as in number 1) than if it is a natural 12 failure (more likely described as number 2.) Muvh like I choose to narrate a roll of 2-fails on an attack roll as a wild miss but a roll of say 13-fail as a glancing blow, near miss or blocked by shield at last second.
I don't do things the way [MENTION=97077]iserith[/MENTION] does. 
