Well I think something more definite than hoping and praying was called for. Let me turn it around, do you think that there was more Snape could have done to protect the message and to ensure that Harry would receive it and believe it? I'm not saying that Snape deliberate failed to get the message to Harry or to try and get the message to Harry, I'm saying this information is not in canon. If something is not in the canon, it's not part of the books. Now the explanation may be as simple as a plot hole, something that Rowling just omitted to put in. But it is so important to the plot, that I cannot believe that she overlooked it. Yes, I do believe that Snape could have done more to ensure the message would be delivered at the correct time, but I'm not the author and I can't change what she wrote. So while I may think that Snape should have been shown enlisting someone in the school like McGonagal or even Slughorn I can't write that into the story. It's not my story. I am puzzled by this seemingly large lack of logic. Perhaps there is something in the books that explains it, but I haven't come across anything yet. I am bearing in mind that Snape's actions are dictated by his creator. Snape actually can only do what she has written in the books for him to do. I think this is something that at the present time we can only speculate about and hope it is cleared up when Rowling publishes her encyclopedia. She is the only person who knows why Snape did as he did.