Error Message in Test

Came in this morning, got into Test and saw this error. Was wondering if anybody has seen this before.

Method ‘get_InDiscount’ in type ‘Erp.Tablesets.OrderDtlRow’ from assembly ‘Erp.Contracts.BO.SalesOrder, Version=10.2.300.0, Culture=neutral, PublicKeyToken=5d3fa3c7105d7992’ does not have an implementation.

Try regenerating your data model and then restarting your app servers.
Verify that your application assemblies folder matches production.

It looks like a missing stored procedure in the database, but this seems unlikely unless someone was poking around in the database.