There is a beautiful Lecythis ollaria tree in Tenom with dozens of those Smurf-house fruit shells lying on the ground, indicating that there should be more than a hundred seeds in, on and under the leaves that thickly carpet the ground under the tree... but they are very very difficult to find. I wonder if it is just as difficult to find L. zabucajo seeds. I think if they were grown commercially, you would have to regularly rake the dead leaf mulch away to have any hope of finding the nuts. I had the same problem with the Lecythis species growing in Dominica.