Had the same "issue". The problem lies within your schema.
You have to add identity to your primary key column:
ID INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
Then you get back the row and you can i.e. create a new object with it:
var x = db.Scan.Insert(Name:"Test", Description:"test", CreationDate:DateTime.Now, DocumentDate:DateTime.Now, ModifiedDate:DateTime.Now);
return new Scan { ID = (int)x.ID, Name = x.Name, ... }
From the Wiki:
If you have an IDENTITY column defined on your table, then the Insert methods will all return a copy of the record fetched from the database, so all defaulted values are set. In 0.4, support for other ways of fetching the inserted row will be added.