If you failed due to a "must" requirement (e.g. you failed to package your classes in an executable jar file) then you will get a very descriptive error message from the assessor stating what they tried to do, what happened, and why they therefore failed you.
If you failed because your cumulative number of points lost exceeded 20% of the maximum possible points then you will only be told the scores for the individual sections (e.g. you might get told that you lost 20 points for Data class, 20 points for Server, and 41 points for Locking, taking you below the pass mark). All you can do in that case is rework the individual sections.
If you try to contact
who2contact@sun.com, they will have to look up your details and then request the information from Prometric. Prometric will then have to look up their details to find which assessing body looked at your assignment and ask them for more information. The assessing body will then have to check their records and/or talk to the individual assessor. I am not saying that this is not going to happen, but I have only ever seen people successfully get responses back when they queried an automatic failure for something they disagreed with.
Regards, Andrew