Motoro sp Peru, would be my guess. I import many rays out of Peru, alot of them are mis-labeled.. You might of heard names like yepezi, pina, nazca, etc thrown around. I believe they are all sub-divisions of the Motoro family. Each one will have a different pattern depending on Age and the Region it was originally collected out of. I get rays labbeled 'Motoro common' which are the same price as Motoros. They come in with random patterns, usually they are beige with brown spots.. or brown, with beige spots. As they grow, the spots will link togethor, and create other patterns. I would really love to have a scientific backing on this, and our company is taking steps to do so. We have invited multiple ichtheologists (sp) to come to our facility, and look at these rays. We are hoping that David Webber will also come to our facility when he makes a trip to Peru, to film a stingray documentary. Hopefully a team of ray professions can shed some light on the situation.
Also, it could of been P. Hystrix. They are EXTREMELY cheap, and are usually beige. Now that I think about it, that's probably what it was, if it was that cheap. Remember if you are buying a ray under 8", it is a BABY. They are super-sensative, and will die for unknown reasons..