Individual transactions aren't found in application logs, they are found in the data store. Also, again, it's important to stress that central logging should be available, just not on all the time. If it's a specific sequence of events that triggers a problem, turn on logging and then ask them to do the sequence again. If they don't need to do the sequence again, then it wasn't really of consequence. And if it happens for multiple users, then customer service should be able to turn on let the developers know to try and find the cause which they can do by adding more metrics or perhaps some temporary central logging.