I agree the lfs is often wrong. The link u gave is not working.
Also the pattern can be deceiving sometimes as the fish have endless variations of stripes but sebae's back stripe is so obvious once you see it.
Otherwise u know have to research shape of head, fins, and etc.. but if the tail fin was outlined with white that would be a give away as a clarkii.
This is only my guess. A better expert can be more definite