Halamaya--
i think your getting confused. Fish of the genus Calloplesiops and Plesiops are often called "salt water betta fish"' or marine bettas. A more common pleisiops in the hobby is Plesiops corallicola, a rather unremarkable, but hardy tankmate, very secretive, and as you mentioned it uses its fins to "perch" upright on the substrate.
Like you i was also not able to find a Plesiops betta, using my usual fish ID websites.While fishbase is not complete- they have spent alot of time outlining fish, so if its a species of Plesiops- it would be listed, but maybe not filled in, and it isnt.
care to look thru 28 species to see what your fish might be?