Will my instinct solar recharge from totally flat battery (turned itself off) if I leave it in the sun or can it only charge from flat using the USB charger? (I don't have my cable with me)

My IS turned itself off and won't restart. Just before this happened I noticed a low battery symbol. I don't have my cable with me as I've been in the bush for the past two weeks and relying on the solar charge to keep it going. In the past this has worked for well over a month. So my question is, will my instinct solar recharge from totally flat battery (turned itself off) if I leave it in the sun or does it need to be turned on (have enough charge to turn on) for solar charging to work?