Parrotfish are known to swim miles per day in the wild. This fish should NEVER be kept in any home aquarium. The Fish Store you purchased it from should be embarrassed for even bringing in the fish in the first place. I would speak to a manager and inform them that you won't give them any future business, and spread the word to anyone else you know who may be a customer. These stores need to be held accountable for being dishonest, and greedy.
The wholesale price on these fish is very low, similar to Moorish Idols, but stores bring them in, mark up the price and sell them to unknowing customers. You are not at fault, your LFS is. I would however, take more time in learning about species before impulse purchases. We've all done it. This hobby tends to make people purchase on impulse. I've certainly done it in 8 years of keeping SWF.
But I would strongly suggest you find a new LFS. This fish does not have a good outlook, as it is unlikely that someone with a 1000 gallon will come in and buy it. I would just get it back before it dies on you, so you can at least get your money back.