You could ask "what was the fallout?", "Did the client get compensated?", or "did you make procedural changes afterwards?" without being as confrontational.

Less people will post about their mistakes if they know they're going to be lambasted for them. We can learn from these mistakes if they're shared or they can be a timely reminder of stakes if we're slipping into complacency. So we probably don't want to discourage such posts (especially since it's rarer for people to want to talk about failures that successes).