Same thing happened to me, i used my cellphone to add to cart at exactly 8am and waited for like one minute, then i used laptop to add manually and within one minute it was in my cart, but my cellphone got OOS later.
My friends told me that the store in their city was FCFS, they all got what they wanted and the resell price on Taobao is like 100-200 CNY more than the retail price, so i guess it's not hard to get.