I guess, eh, MAYBE I can find someone else, but chances are, he won't want to join. Honestly, you can't expect or even always hope for a specific number of people to show up to your RP. I tried that once, it didn't work, at all. Usually, one of two things happens in scenarios like this (I've seen other people do something similar, they all failed)
1.) The RP doesn't get enough people, and those who did join end up waiting forever, the RP dies without a single IC post.
2.) The RP gets TOO MANY people trying to join, and has to tell the excess people to leave the RP... which doesn't usually result in a happy person who won't hold a grudge against the OP for doing that.