Oh I can relate to this a bit. Mine will sometimes go through plants and will stop moving lifelessly hanging out of plantsJinx, some of my kuhlis liked to hang out in tall or floating plants. Scared us all when I saw them do it the first few times. I reached in & touched 1 & we both freaked out! Then it got so I could reach in for water changes, etc. & they never moved. Maybe the most mellow fish I've kept. Mine were semicincta (a species of striped). My black p. oblonga in the same tank were not so mellow, always active. Which species do you have?
They once hid sooo well I thought I lost most! Mine also haven't tried jumping out of the tank, yet.
As for species, I have no idea.