I can actually understand if the console and games were in working order, that they might ditch the non-working controllers if they had others and didn't want to repair the ones that weren't working so well (if at all). 

When did they contact you about this? If it is the console I referred to above, the left you a positive on the 19th so presumably were happy with the working of of things at that point and then ditched the controllers after assuming all was good. It may or may not be the case, but circumstantially suggests it may be a problem that developed after they received it.