When fighting a character twice in a row (for instance, when you lose the first time), familiars will not appear in the post-battle stats. I have tried this countless times and started a thread a while ago to document the issue. I even provided screenshots. I now realize it occurs every single time you fight a character twice after not killing him the first time. It occurs on both Fire and Steel familiars, and it does not matter whether or not the familiar in question deals damage, receives damage, does nothing, or does everything. It is not affected by Phantom Link taking damage away from the familiar, nor does it only happen when PL isn't involved at all. The only factor that seems to have an effect is whether or not the character your fighting has been previously attacked by you. I was not able to test having the first fight inflict zero damage and the second fight kill him, nor do I plan to.
I tried asking an admin some time ago to let Jon know about the bug, but I believe the response was something to the effect of, "Jon saw the thread... if he cares, he'll fix it." So, I'm trying once again to get this issue raised. Hopefully, it will not be ignored again.