Figured it out:
In the first form:
DoCmd.OpenForm "hhroster", acNormal, , , , , Me.file
Second form OnOpen:
If Not IsNull(Me.OpenArgs) Then
Dim rs As Object
Set rs = Me.Recordset.Clone
rs.FindFirst "hhroster.file = " & Me.OpenArgs
If Not rs.EOF Then Me.Bookmark = rs.Bookmark
End If