Glad to read it didn't have you off, stuff of nightmares. If I were in your shoe's I'd be trying to find the failed chain to see if I could figure the cause, and I'd check the sprockets for any signs of damage caused by something having wedged in there, or any damage to casings due to chain letting fly. Any input just before failure - accelerating and gear change for OTake may have caused whatever weakness was there to fail (rather than a stone getting jammed). With 5K on the bike it should have been OE chain, but maybe it was a poor quality replacement. What year is the bike out of interest?
Sean