Do the numbers still exist in your google contacts?
Google recently terminated support for new configurations of gmail using Exchange Active Sync for unpaid accounts. In theory, existing configurations will continue to work, but there have been some problem reports.
I've seen several mentions of the problem you describe in the last few days and so far, they've gone unresolved as far as I can tell. The root cause may be in google's termination of AES support.
Facebook contact sync may also be a suspect.
Thank you for sharing this information, it is the first answer that remotely seems to apply to my situation. No the numbers do not exist in my google contacts either.
Seems to be twofold problem
1. exchange and gmail mail are no longer syncing
2. contacts added directly to my phone have disappeared too
It just all happened at once.