I can see similarities to some uncolored fry, so it may be that this fish is the same species/strain as L10a. It does happen that fry from L10a don't develop the red color on occasion.
I can see aspects of your fish which could make me suspect it is either an Hemiloricaria lanceolata or a poorly colored L10a.
If I had to bet on it, I would come down on the side of a poorly colored specimen of L10a.
All the living H. lanceolata I have seen in person had distinctive patterns and were not as flat as your fish.
It is even possible that it hybrid between the two. There are two strains of L10a. One retains very good red color and stays very flat bodied. The other one is duller and has a more rounded body shape. The latter type has become the most widely bred form.
I have 10 L10a and some are plain brown. They all started out as red juveniles and I have managed to breed them but not very successfully. My young ones were also very red but they lost that brick red as they matured with the group along a continuum between medium brown and reddish brown.