Start AP with hidden IP

There is a flag (ssid hidden) for this listed in the AT commands for the ESP8266.

1. AT+CWSAP_CUR – Current config of softAP mode
   AT+CWSAP_CUR – Set configuration of softAP mode, won’t save to Flash
   Example AT+CWSAP_CUR="ESP8266", "1234567890", 5, 3
   Command AT+CWSAP_CUR?
   Response +CWSAP_CUR:, , , , ,
   Parameters
   string, ESP8266 softAP’ SSID
   string, range: 8 ~ 64 bytes ASCII
   channel id
   
   0 OPEN
   2 WPA_PSK
   3 WPA2_PSK
   4 WPA_WPA2_PSK
   
   maximum count of stations that allowed to connect to ESP8266 soft-AP
   range: [1, 4]
   Broadcast SSID by default
   0 broadcast SSID of ESP8266 soft-AP
   1 do not broadcast SSID of ESP8266 soft-AP
   Command AT+CWSAP_CUR=, , , [, ][, ]
   Response
   OK
   ERROR
   Parameters The same as above.
   Notes
   This command is only available when softAP mode enable.
   ESP8266 softAP don’t support WEP.
   This configuration will NOT store in Flash.
   Espressif
   
   

https://cdn.sparkfun.com/assets/learn_tutorials/4/0/3/4A-ESP8266AT_Instruction_SetEN_v0.30.pdf