LOL! I was thinking along the same lines...’don’t let me forget to take my wallet when we get off the boat, there might be some interesting ‘establishments’ a sailor can patronize...’
http://www.youtube.com/watch?v=aC-A6SP3EsQ
1st off, it is very possible that anyone, anywhere, could be carrying just about anything. They could happen to have change in their purses. Why would it be shocking that some things Europeans would have in Europe or in their settlements, from whence they shoved off, would be on their persons in a strange land?
2nd, coin-collecting was not a big thing until the late 19th century. Sure, some people bothered with it prior, but it just wasn’t a big deal until then. So while the coin may indicate a fool losing a neat old piece in the last century, it’s doubtful it would have been “dropped” by someone who happend to collect in the previous century or 2.
3rd, the coin was in several inches of earth. Not knowing the exact circumstances of the ground when found, assuming everything seemed “natural” and undisturbed, this would indicate natural erosion and shifting such that the coin ended up buried from simply being dropped, exposed to the open.