I think your squash may have shriveled up because it was not pollinated. When female squash flowers develop, they have what looks like tiny squash on the back of them (this is the ovary). If it is pollinated and successfully fertilized, when the flower falls off it will keep growing into a larger squash. If not, then the ovary may grow a bit more (to a couple inches) then shrivel and fall off. To avoid lack of pollination you can use a paint brush to move pollen from freshly opened male flowers (those without the "baby squash" ovary) to the female flowers. Plant a few squash plants in your garden to help ensure that you have male and female flowers blooming at the same time. I hope this is helpful!