The remnants of an alien 'protoplanet' could be hidden deep within Earth

The paper cited states, "From these results19, we found that a significant amount of TMM, 0.017–0.026 Earth masses (M⊕) (Extended Data Table1), could have entered the lower mantle layer, which is comparable with mass estimates of approximately 0.01–0.06M⊕ for the LLVPs14,20. However, both thermo-dynamics and material mixing are sensitive to the setup of numerical models, including equations of state, numerical resolution and the hydrodynamical method (Methods).",

I am not sure what the proto-earth mass was used in the simulations reported here and density compared to Theia modeling before the giant impact. I have read some reports where the proto-earth mass before Theia impact ranged some 0.6 to 0.9 present day earth mass. The Moon that formed after the giant impact likely was a smaller mass Moon too, not much reported on questions like this it seems to me.

When it comes to the exoplanet lists, there are no confirmed exomoons that formed via a giant impact it seems.