Ok, I think I understand. If the first n probes for a given hop don't get a response, you will have n asterisks ahead of the IP if/when it actually does respond. This is because tracert doesn't know the IPs or response times of the hops until it gets a response back for that hop. Sometimes it's possible to get the false impression that it is discovering IPs and then pinging them. Thanks for the clarification!
Incorrect placement of asterisks for probe timeouts