Ipad went Black

Very scary for me but I was flying today in Canada, mini 2. Usually all good. Everything charged up. When all of a sudden my ipad goes black. I had zero screen info or anything. The drone was way far away but had lots of battery. I had no way of knowing in what direction it was flying so I was basically f***ed. I initiated RTH and after about 3 sweaty minutes it descended right to the exact spot it took off from. Great system DJI has as far as RTH goes BUT what the hell went on here?? Everything was updated as far as I know. But can anyone elaborate? My equipment is all current. WTF??