If I remember correctly, from reading the original story that broke this news, location data at the rectory he was living in correlated with location data at various conferences he attended. That was sufficient to identify the anonymized data as his phone.

> The Pillar correlated a unique mobile device to Burrill when it was used consistently from 2018 until at least 2020 from the USCCB staff residence and headquarters, from meetings at which Burrill was in attendance, and was also used on numerous occasions at Burrill’s family lake house, near the residences of Burrill’s family members, and at a Wisconsin apartment in Burrill’s hometown, at which Burrill himself has been listed as a resident.

https://www.pillarcatholic.com/p/pillar-investigates-usccb-g...