The most probable result is death on first sight. But if you always go with the most probable result, you don't have a story. Besides, considering certain historical events, it seems to me that having the most likely thing always is very unlikely.
Sam would, of course, know all the places to hide things. And if you want to hide something in your living quarters, there are only so many places you can choose. I'm pleased that Sam knows them all because, of course, Sam WOULD know them all. His easy assurance and efficiency here reflects his character in perfect fidelity.
In a way I hate to say it, but the perfect hiding place is like the perfect code or, I suppose, the perfect crime: Completely random. Choose to bury your stash of papers at the third white rock along this fence in an area that has nothing to do with you, except that you can reach it in a reasonable amount of time, and (assuming you don't go to check that it is still there until you need it) the odds are that even Sam won't be able to find it, even if he knows what you did. Except that being Sam, he could probably psych you into going to check, and then he could follow you.
That brings up the problem of X Marks the Spot. Because if you make up a little treasure map, then you have to hide the MAP in some place where Sam could find it, and that defeats the purpose. Otherwise you memorize your "random" location and don't make a map. But in that case, if you want someone else to get your stuff once you can't, they can't either. Or you forget where it is yourself. I have a nice small handful of 1400 year old coins that somebody hid in a safe place, long long ago, and never found again. They find these all over the place. People hid them in safe places and forgot them so often that to this day you can get your own bronze Roman small change, if you want it, and the coins are generally too small, cheap, and common to be worth counterfeiting.
Yup, it's probably easier to outsmart yourself than it is to outsmart a pro like Sam.