As I understand it, the properties of a particle exist in superposition in the wave function until a measurement forces a the wave function to "collapse" to one possibility, and the particle continues to have that value for the property until it interacts again with something else. But for someone who doesn't know that the particle has been previously measured and that it has not yet interacted again, then for that person, that property is still in superposition and is inherently unknowable until there is a measurement. So it seems there is two states of knowledge that seem to be in contradiction. For one person, the value is determined, for the other it is inherently unknowable. Both conditions for both observers seem to be able to exist at the same place at the same time. What's going on? Are properties inherently intrinsic to the particle or not? How do we know whether any particle we might ever measure has not already been measured by someone else or has not afterward interacted again?