The thing is that Sasuke as all Uchiha has a sharingan...and that will see through the genjutsu, maybe even reverse it, although I think that's impossible without sage chakra, but still...
So does sasuke knows all jiraiya's technique..? how can he fly to counter jiraiya's swamp if he doesn't know anything on jiraiya's arsenal.? sage mode.? does sasuke knows that jiraiya has that kind of power.? YOu're just assuming that sasuke will never let jiraiya to go into sage mode even if he doesn't know anything on jiraiya.. amaterasu.? can it really burn/hit jiraiya.? jiraiya knows how to use a bunshin in any situation.. But then again, jiraiya can counter the amaterasu with his hair mane jutsu to cover his entire body and seal it immediately.? imposible.? nahh..
If jiraiya can manage to summon pa and pa and sasuke will be good as dead.. One frog song and sasuke can't move, and then what.? jiraiya will going to make him a frog.. and we seen that the hermit mode jiraiya can do a kage bunshin, so you can't assume that it was the original who got caught by sasuke's amaterasu..