find my iphone got disabled on stolen phone

So my iphone 6 got stolen few days ago and find my iphone was on and the thief didnt turn off my phone so i followed him on the app for a while then he turned the phone off and i enabled lost mode , i didnt click erase button but when i refreshed in find my iphone it was on erase mode automatically , then few hours later i got 3 emails , first that lost mode was enabled , then a sound was played , and the last email was find my iphone disabled and my device was gone from icloud , so how find my iphone was disabled? Was it because of erase mode? cause it said i cant access my phone anymore if i enable erase mode. Or they got arround my passcode and apple id and somehow unlocked the phone?