isDeleted=True is not working in SOQL query

Did you check "Deleted and archived records:" as "Include" ?

And as for the Developer console, you have no way to do it. You can do with Apex using SOQL with the "ALL ROWS" option, but the Query Editor on the Developer console doesn't support it.

Are you using the "QueryAll()" API call when you try to retrieve the delete records? Using the regular "Query()" call won't allow you to retrieve delete records. See the API documentation on the "QueryAll()" API call here:

http://www.salesforce.com/us/developer/docs/api/index_Left.htm#StartTopic=Content/sforce_api_calls_queryall.htm

Thanks!!!