When a pine tree dies, most of the sap is retained in the core of the tree, particularly the stump. In Florida we call it lighterwood because you can chop off a few slivers and start a camp fire with it. It'll catch fire quickly and burns hot.
I have found that every piece of pine driftwood is an old piece of lighterwood. If you drill a hole in it somewhere that won't ruin its appearance, it will likely be hard as a rock and have a strong (and pleasant) pine smell. But, it won't smell at the surface and might not even if scraped with a knife.
If it does contain old sap, it is loaded with terpene compounds which can be very toxic. There was a pesticide used years ago (Toxiphene) that was derived from alpha pinene, one of the main compounds found in lighterwood stumps. There are dozens of other compounds that make up the sap. Part of the reason that the lighterwood lasts so long is that it's toxic to termites and other wood eating critters.
