AnalogRead(0) always returns 0 on RFduino
Without RFDuino specs handy, I'm guessing - but I think it's likely - that the A/D converter gets shut down in an ultra low power sleep and requires some amount of time to wake up. The mis-reading pin, pin 0, is the one your sketch reads immediately on waking. That read call probably takes long enough that the A/D wakes up by the time your read pin 2 so it gives a better reading. 

Try switching the order in which you read the pins and see if pin 2 mis-reads if you try to read it immediately after waking. If it does, the cure may be as simple as a 10-100 uSec delay between waking and trying to read any analog data. I just pulled that number out of the air; you might start with a couple of milliseconds and see how low you can make it before you start to see errors, then double that amount.