What’s the worst possible outcome now? If the tobacconist meets a dustmen entourage that has already pieced together something like the true story and has with them his full description from the man at the committal wall, then the only new useful information they’ll gain is that he is now dressed in a dark vest and boots. The rest, the part about Clerk’s Ward and the claims of great sorcery and power, should all be to his benefit and tend against continued pursuit. And they walked what, ten minutes from the tobacco shop? So he has at least twenty minutes to work here.
The greater danger is that the enemy is still watching this place. But having already come here, he should proceed with as thorough an investigation as he can.
How does this fit in his five scenarios?
Actually, first. He should move his hands about every possible item and bit of trash in this alley. Any one of them might be the locked journal. Certainly if he were himself now fleeing a threatening adversary, with any hope of recovering his memories tied to his future self’s finding a hidden journal, he would have summoned the utmost of his wits to find a way to safely dump the thing nearby.