Where is FLStudio finding my Midi instruments?

Sorry if this is a n00b question.

I import and work with midi files on FLStudio. Once in a while, I will get a track with a missing midi instrument - no big deal as I'll choose another midi instrument in FLStudio and keep working.

Though this time, when Fruity LSD opens and I double click the track that has (none), I get a window that opens which says "select percussive patch" (which is a percussive instrument missing) and I have several other selections of instruments which I can't find within FLstudio. I can choose them and FLstudio will play the audio, but then the Fruity LSD will immediately go back to that track and say (None) when the audio is done playing and I try to play it again.

I have 2 questions - where the heck is FLStudio finding those instruments to use in that track and how can I get FLStudio to save what I am choosing so I don't have to keep going through the process of choosing an instrument to play the audio again?

Truth be told, the instruments actually sound better than what comes with the stock FLStudio software so I would like to be able to use them if needed in the future.

I have a NEW Window10 system. I have no other audio software on the machine and no other crapware from the manufacture loaded on the PC and have a clean install of FLSTudio 12.4.1 producer edition.

I'd appreciate any insights anyone may have.
Thx.