Using an INNER JOIN Should not cause the recordset to disappear. I see no problem with the SQL Statement you have provided.
What happens if you click the test button before clicking the OK Button? Does the SQL test OK.
Sometimes I have seen Recordsets disappear in Dreamweaver for no reason, often saving the page, closing it and reopening it will bring the recordset back into the list.
As for the exclamation mark next to DataAssist Search, the red Exclamation really only means "there *may* be a problem" when Dreamweaver inspects the code, it sees something that is "not quite right". It means the page May run smoothly, or it may not. If it doesn't, the nit's time to worry about the exclamation mark, if it does, ignore it.