Lin, the size and shape of the fruit does look like a Passi, but the inside looks much more like a cucumber to me. Passi's have thick skin and orange pulp with black seeds in it.
There is a variety of cucumber called 'Lemon' that has fruits that size, shape and color. I used to grow them in Utah, and they are delicious. If it were me, I'd try a tiny taste of the flesh and see what it tastes like.
Cucumber (Cucumis sativus 'Lemon')
Also the leaves look more like cucumber or melon to me. It might be a 'pocket melon' but they tend to develop stripes.
Dudaim Melon (Cucumis melo subsp. melo)
Candice is it possible that your dirt pile used to be a compost heap? That would explain the presence of odd seeds in there.
