I remember this coming on the news at the time. Because of the cold weather, there was unprecedented demand, combined with a supply chain issue.
Eastern europe was having extremes of cold and their useage was well up aswell.
Something happened, a supply pipe went pop, or a pumping station exploded, somewhere in eastern europe, I don't remember right now.
Basically, it was a set of unusual incidents, all occuring at the same time, not really an issue with lack of storage.