Where is the crawlspace access?

The dining room addition gets no heat in winter and is unusuable. Also, there is no access to the crawlspace under the dining room floor, so I suspect it has been covered up.

The styrofoam smeared with concrete stucco looks suspicious and sounds hollow, so I decide to break off a piece to investigate.

There are cinder blocks behind the styrofoam, and the bottom ones have been properly sealed with tar.

With this information, I suspect that the crawlspace access is probably in the finished basement, covered with drywall.