If I understand you correctly you intend to use this information only internally within your organization to detect possible fraud?
Regarding checking for IP and browser I would guess that most people doing these types of fraud work through different proxies to change their ip around and use incognito features to "hide" their browser.
Some people here seem to miss the fact that a question was raised. It has nothing to do with our own personal believes of password treatment and best security practices.
If one agrees to what the person asking the question wants to do or not is not the point. The question was plain and simple:
Question: If it is determined that the fraud-detection ability of being to retrieve passwords is necessary, what are the best practices for storing passwords securely but in a way that is plaintext-accessible?
He doesn't ask IF it's 100% secure. He asks for practices of making it as secure as it can be.
Yes, it will most likely suck and be impossible to protect with a 100% success rate. But IF IT HAS TO BE DONE, how could he do it as secure as possible. There will ALWAYS be a way around anything not encrypted with a, as of yet, unbroken hash algorithm. It might be more or less dramatic and might require some C4 to get into a server room 100m bellow the surface and kill 10 armed guards hardwired to a system that kills them if they even try to leave the room (so that they themselves can't steal the information and leave).
But it's still not the point of the question. He wants to know how to store PLAIN TEXT passwords as securely as possible. From whom isn't very specified and if he is the only one handling this system (and we assume he can trust himself) the only ones he has to protect the data from are outside parties. If not, then internal parties will also have to be taken into account.
Does it suck to store sensitive data as plaintext? HELL YES! Does the person asking the question deserve to know that? Yes!
Do we answer his question by only stating that? NO!