Welcome to Pond Boss alucard!
It is most likely the species repopulated your pond either by migrating up the drainage that leads into the creek, or washed into your pond from another body of water further up the drainage. It is highly likely to impossible the eggs survived in the mud. If the brown bullheads died off, everything did including the eggs as they are about as hardy as they come.
I am aware of perhaps two or three hatcheries that sell brown bullheads. However, they are all northern hatcheries, with the closest I can think of being in WV.
If other fish are naturally finding their way into your pond, they are also bring their parasites and diseases with them. Your only choice may be to source brown bullheads from another pond. Just realize the risks and decide how bad you want bullheads back in your pond. Have you considered channel cats instead of bullheads? They are much easier to source from hatcheries and cheaper as well.
