That's exactly it - if it had been left in the sun in the supply chain, once it has left NN it goes to all sorts of different warehouses, then to the pharmacy who at some point stick it in their fridge.
For all we know, the person(s) that had the problem could have left it in their car or something. I've been known to do that, falls out of portmanteau into the footwell and don't think about it for ages afterwards. Fortunately never insulin. In the olden days I used to collect scrips from chemist near work at lunchtime. In handbag then till approx. 7pm or later, when I got home. Never used to worry and I ain't dead yet !