Not due to sync or update. Itunes showed there were no backup files on this computer even though i regularly synced and backed up.
Now itunes doesn't find the iphone at all.
When it happened, i was running an old ios, so did not have icloud yet. I updated the ios today, and it works fine, but the contacts are still missing even though everything else is in icloud. THis was to be expected of course since they were not in the device when i updated.