I'm looking to have a query created that will send me a list of IT Assets (Workstations) that have been disposed of in the last 30 days. 

We've disabled the option that disposes IT Assets if they have been removed from Scope of Management in Desktop Central. When enabled it removes all ownership from the Asset and causes problems. But we still need to know when an asset is disposed of so we can remove it from Scope of Management manually. That's what the query will provide me.