So LFS often sell lots of loaches as kuhlis but they are often one of four or five different species now I know the one you have is brown just like the ones I have but they are called the black kuhli loach no idea why since they are brown but that's what they are called
I am 100% it is not a black kuhli loach as when i brought it it was in a tank with normal blacks and it was very different, also i have black kuhlis in my tank and it aint the same. its hard to see from the image but it is very very very thin.
I was searching and could it be a Pangio anguillaris or a similar species
Does it have a forked tail or a rounded one?
I know there is a type of swamp eel that is often caught with khuli loaches and shipped off accidentially with the wanted khuli loach.
The loach has a normal tail that kuhli loach have. i was just looking at the loach closely and it is two shades a light brown on top and a even lighter colour on the bottom side. similar to this picture of google
I think you are right in that it is probably anguillaris, I have an unknown Khuli that I got in a shipment some four years ago now I think it may be Filinaris? got the usual striped and then an oddity! strangely all the striped died off ( I think they had internal parasites ) but this one is still going strong, may have to get a few friends for it.