He let everyone know by his tweet saying,
Everyone! I got my instagram back! Please follow me at ------------leedonghae------------- http://t.co/HwsbGJxUNR— Super Junior ??? (@donghae861015) July 26, 2014
It seems like he was somehow about to get his old ID, and he sounds excited to have his ID back! If you don't follow him yet, you can do so now here.