It's amazing how 100 CC can just disappear in a 3.5 acre pond. If you start to consistently feed at the same time and place each day, if any are in your pond you will find out shortly... I would guess there are still plenty of the 100 still left and probably a nice size by now... If they have spawning structure, you may have many more than 100...
Getting forage fish to establish themselves in a predator rich pond can be tricky. FHM are about impossible to keep in a pond with predators let alone get established once predators are present... So I wouldn't waste your money on them unless you just intend for them to be a quick snack.
Besides the pallets, do you have any other cover present in your pond? Aquatic vegetation, tree tops, etc? Also, are there any substantial shallow areas? In my experience, it is VERY hard to keep a population of just about any forage fish species present long term in a pond that has extremely steep banks with almost no shallow areas. It may keep cattails and SAV under control, but it doesn't help forage fish to prosper...
HBG are not good forage base as they do not reproduce much. You may want to consider stocking pure strain BG into your pond.
GSH are probably your only serious options for solely forage fish in your pond. There are several other species but they are not available commercially and require they be collected from the wild.
