When the Scribe Scroll feat's benefit says, "You can create a scroll of any spell that you know," it's not supplying mechanics. Instead, that sentence serves as the beginning scroll scriber's introduction to scribing scrolls. While that statement is technically inaccurate, this reader is willing to forgive that impropriety and say that it's close enough. This reader totally understands if another reader wants to read it differently, though, but if that other reader does that other reader must contend such inaccuracies throughout the game and, perhaps, alter the game to match its hyperbolic mandates (e.g. the even more deceptive benefit of the Craft Rod feat: "You can create magic rods").
Anyway, that said, a wizard prepares the spell that's to be triggered to create the scroll. Then the wizard, in the act of creating that scroll, triggers the spell (see here). A wizard can have in her spellbook a spell that's too high a spell level for her to cast (see here), but, as the wizard doesn't have spell slots yet suitable for preparing that spell, the wizard can't trigger that spell during the course of item creation.
If I may be so bold as to make an assumption, I think that the question that may be being asked here is actually this question: Where does the game say that between triggering the spell that's to be scribed onto a scroll and actually scribing the scroll that the triggered spell's caster level is the same as the scribed spell's caster level?
And you'd be right: The game doesn't provide that detail. However, before the skilled reader can make hay out of that unmentioned detail, on Magic Item Creation says that a wizard "can create an item [in this case, a scroll] at a lower caster level than her own, but never lower than the minimum level needed to cast the needed spell" (see here). Be careful here, though, and ask the GM for clarification! This GM has always ruled that this sentence means that a wizard can't create a magic item at a higher caster level than her own but only up to a caster level equal to her own.
(That is, this reader suspects that the sentence's intention is that A wizard can't create an item at a higher caster level than her own, but never lower than the minimum level needed to cast the needed spell, making the sentence much more palatable with both of the opening clause's modifiers (can to can't, lower to higher) flipped. This reader understands if this is a bridge too far for other readers.)
As the question notes, triggering that spell appears not to be labeled as a prerequisite for scribing the scroll. However, it wouldn't matter if triggering the spell were labeled a prerequisite as skipping triggering the spell by increasing the Spellcraft skill check DC by +5 to create the item, as the question also notes, isn't an option anyway.