OK I have seen just this week that there might be an issue with the REST Find Operation and a service published from an MSD vs. and MXD. Specifically we are using SQL Server 2008 and ArcSDE 9.3.1. We noticed a possible issue with text fields that hold numeric values like 1234. I have not tried to query the area or length fields.
For now try and publish your Map Service from the MXD and see if it works any better. If it does then for now I think you have to use the MXD. We wanted to use the MSD because of transparency issues, what do you need the MSD? Are you using SDE? If so what version and specifically which RDBMS are you using (SDE, Oracle, etc...)?
Drew,
FIND will find values such as "123456" as long as this value is stored in a string field. is that the use case here or is that value stored in a numeric field?
Ravi