You can always bring the Pleco back to a LFS, try to sell it on here, or somebody local near you will probably take it.
I have a common Pleco and it is brown with black stripes or dots. I got it for one dollar at the pet store and when or if it actually does get up to a foot or even TWO then I know they will take em even if I have to give it away. ( I have asked at least a dozen different pet stores around me in Chicagoland Area )
It's better then stunting there growth and not giving them enough space. Plus they have a pretty big bio load and get cranky when they are older at least thats what I know from friends and past experience when I was younger and had em.
I bought it for a dollar and I will probably find a pet store that will trade me for other fish, plants or store credit or might just take it off my hands.
So if I can have a fish that is helping me clean up some extra food and stuff in my tank, looks cool, is really cheap and is docile especially when young and I have the potential to get other fish or plants that would cost more than I am happy. Lol
Remember just ask the LFS and see what they say or post it on here and see what happens but you will have a while to decide on what to do and what route to take.
Please please please do not ever put him in your local waterways especially if you live where it gets cold. They will not survive the weather at all this shouldn't matter though as you are never gonna put fish in your local waterways right? Lol
Just my opinion hopes this helps.
Bill