Laundrie left a new cellphone at home before he went for a hike in the Carlton Reserve on Sept. 14, Laundrie family attorney Steven Bertolino confirmed to ABC News.
The FBI now has the phone, according to Bertolino. The FBI had no comment to ABC News.
Petito went missing on a cross-country trip, and her parents, who live in Long Island, New York, reported her missing on Sept. 11 after not hearing from her for two weeks. Authorities confirmed Sept. 21 that her body was discovered in the Bridger-Teton National Forest in Wyoming.
WATCH: Tracking the Gabby Petito disappearance