The fact that we know where the gaps in the fossil record are is because of evolution. The theory of evolution predicts a specific nested hierarchy, and it is this predicted nested hierarchy that tells us where the gaps in the fossil record are. For creationism, there is no expectation of a nested hierarchy and therefore no gaps. In the creationist model there should be a mix of many types of features without requiring a nested hierarchy. You are just as likely to find fossils with a mixture of mammal and bird features as you are a fossil with a mixture of mammal and reptile features.
I also don’t see how you can look at a fossil and determine that it had no ancestors. What method allows you to do that? Also, how can someone determine that our fossil collections contain a specimen from every species that has lived? The problem is that people treat the fossil record as a complete record of life. It isn’t. This is proven almost every month as a new fossil species is discovered.