The photo was likely just the lead that tipped them off to building. After that they were likely able to confirm it through other means. It's like looking for

The photo was likely just the lead that tipped them off to building. After that they were likely able to confirm it through other means. It's like looking for a needle in a haystack - the hard part is finding the needle, what's easy is verifying that what you have in your hand is a needle.