No doubt Tom's wealth of information came from Fredo

How would Fredo, last sighted walking in a daze amongst the rebel uprising chaos even connect with Roth's people
1. If he did come with them how did they find him in all that chaos?
2. Who would know their relationship Roth in a coma was in no position to tell anyone anything
3. Why would they even bother looking for him, needle in a haystack scenario, their priority would have been sick Roth and getting out