Good morning, what sdk and softdevice version are you using and two things, it can´t reconnect because you have error when try to reconnect, mobile device don´t find board or what?
S110 nRF51_SDK_10.0.0_dc26b5e,when try to reconnect ,it have error 257,after reboot nRF51822 or reopen apk,they can reconnect, this discovery on some android phone,but someothers it's ok!