Question: Would Pilfering Hand be affected by Displacement, Blur, Mirror Image or other types of effects that generate a miss chance for attack rolls, when attempting to disarm?
I would say so. The miss chance the spells create are due to either a visual effect or the target not being where you expect them to be (arguable still a visual effect). Like many spells pilfering hand depends on line of sight so your abilities with it would be affected.
Many things you do with Pilfering Hands require a Combat Maneuver. According to the CRB, "Combat maneuvers are attack rolls, so you must roll for concealment and take any other penalties that would normally apply to an attack roll." So yeah, concealment applies.
Other things you do with the spell require skill checks. There don't seem to be any rules for applying concealment on skill checks (other than Stealth). Maybe I missed something; I often do. But it looks like it might be DM's call on Pilfering Hands used for pickpocketing. Maybe the precedent that concealment applies on other uses of the spell should guide the decision.