I'll use my study on the use of stumps for trail markers as a relative example. If there is no prior evidence that would give you the suspicion this "Sign" has the ability lead you in the direction of a cache, then more-than-likely it wasn't used as one. However, because knowledge of the extent of possible uses for varying signs as trail markers is limited, there may be a slim possibilty this could be one. If it is, you will potentially be the one of the first to recognize it for what it is, so document your find. Otherwise, it's a pretty carving of Pan and that's something to enjoy as well.
Clay