If you claim the device using particle device add <device-id> using the Particle CLI (or using the Web IDE) it can send an email to the original owner. Once they click the link to confirm transfer, it will be transferred.
You can also use the force claim process with a device connected by USB. However, with the P2/Photon 2, you need to make sure the device is unplugged for a while (overnight should be fine) otherwise force claim does not currently work correctly.