No wonder you're baffled. In Hell's Bright Shadow, the first part of the Hell's Rebels adventure path, includes, like, over 20 scrolls, and literally none of them say whether they're arcane or divine and literally none of them have a caster level. That's an oversight that costs the GM valuable time. You've my sympathy.
On Magic Item Gold Piece Values, in part, says
Since different classes get access to certain spells at different levels, the prices for two characters to make the same item might actually be different. An item is only worth two times what the caster of the lowest possible level can make it for. Calculate the market price based on the lowest possible level caster, no matter who makes the item.
So, yes, the game expects the GM to Dumpster-dive for the lowest spell level-and-caster level combination and use that for magic items, including potions, scrolls, and wands. (Those are all included in that section.)
As none of the scrolls in In Hell's Bright Shadow even labeled arcane or divine, the GM can go with lowest of either. That is, the GM finds the lowest level arcane or divine caster that can cast a particular spell and the scroll becomes that kind of scroll—arcane or divine. (To mix this up a little—because this will result in a lot of arcane scrolls—, a rule can be imported from Pathfinder's antecedent Dungeons & Dragons 3.5 and the GM can roll d% whenever a scroll's found with 01–70 meaning that the scroll's arcane and 71–00 meaning that the scroll's divine—see here. Of course, in this case the spells on the newfound scroll must actually be on the appropriate kind of list at some level.)
Thus, when the PCs in In Hell's Bright Shadow a scroll of misdirection, the GM can go to the spell misdirection and pick the lowest caster-and-spell level combination (that would be wizard and 2). The scroll becomes the much more descriptive arcane scroll of misdirection (2nd-level spell at caster level 3).
However, that can be a lot of work, and the return is very small. I find it difficult to believe a group of players would mock a GM if an arcane scroll of heroism is found to have a caster level of 5 (as if scribed by a wizard) instead of 4 (as if scribed by a bard). I mean, that's Brian from Knights of the Dinner Table kind of stuff. Here, perfect really is the enemy of good, and close enough is sufficient.
By the way, the above rules also mean that by default a potion of lesser restoration has a market price as if its caster level were 1 and its spell level were 1 (i.e. 50 gp) because the spell lesser restoration is a 1st-level paladin spell. That's okay. Low-level dudes need those most of all. (And the paladin doesn't need the feat Brew Potion to brew potions of lesser restoration; he can work with another creature that possesses the feat Brew Potion, and together they can brew such potions using the paladin's caster level and the paladin's lesser restoration spell.)
