2004 Ford Expedition 4X4

I recently had my 04 expedition interior detailed and while it was being detailed the detailer must have switched the drivetrain to 4x4 high. I didnt notice it when I picked my truck up and took off on the highway with it in 4x4 which I know your not supposed to do. About 5-10 miles later as I pulled in my driveway I felt/heard a grinding noise and it felt like it was locking up. Thats when I noticed it was on 4x4. Immediately I switched it to 2 wheel drive and it operated fine. I continued to drive it for two days and it still operates fine in 2wd but what is the possible damage? Transfer case, transmission?