Snape - it seems like a shame to just let dumbledore disappear into the ether after all you had in common. I know you probably have enough mates, but it's always useful having one more - even if it's because he may have single friends he can introduce you to (if not straightaway)
I'd get in touch, say it was great meeting him, no spark which was a shame and you're still up for geocaching or whatever in the future as he's such a lovely guy. If you feel like that, that is. As I said, he may have big handed friends.