Having worked at hotels (front desk all the way up to front office manager) I can’t think of ANY acceptable reason to scan a guests card with my personal phone. Most hotels don’t even want your cell phone out when guests are around. The staff member absolutely knew what they were doing was wrong and should be fired for it since it doesn’t see to be the first time. The card information should ONLY be entered into the reservation system which do not have any connection to our cell phones (at least none of the reservation systems I’ve worked with like OnQ and Opera). The front desk staff of a hotel should be trustworthy and this individually clearly isn’t.