RFID does not have the same power requirements Bluetooth does, the power requirements for Bluetooth are described in detail in the spec; it's not something you can get around. If nothing else, unlike RFID, Bluetooth does not have a totally unpowered "sleep" mode, that can be woken by the Bluetooth protocol itself. If your device is awake enough to receive any signal at all, it is drawing power. In fact, it's drawing very nearly the theoretical maximum you could harvest from ambient sources for the dimensions of the device they are describing... and then said device has to actually power up and send besides (not to mention the theoretical maximum is a good order of magnitude higher than what you'd see in real life usage).
There's a difference between "this concept is theoretically possible" (what you describe) and "this idea, as described and designed is workable in real life" (which is what the iFind people are, erroneously or fraudulently, arguing.