If I were Siri, with all the abilities a TITAN possesses, I'd probably attempt to acquire the egos of egocasted fall evacuees. Siri could do this by hacking into dead ego storage, backup services, or simply buying the dead storage. Once in possession of the egos, Siri can do whatever it likes. Siri will likely be capable of reading memories directly from a stored ego, without running it.
A paranoid TITAN shouldn't make mistakes that could reveal it to anyone except for other seed ais. Therefore, the petals should work perfectly every time. There is a way to still have defective petals, though. If transhumans start tinkering with it, they could introduce all sorts of problems.