Not dealer's problem - yours. You should have verified when you received the amp and discussed with the dealer then. Not now. Sorry, way too late. Dealers are people too. People make mistakes. Bring it to their attention within a reasonable time frame (1.5 years is not reasonable; more like within a few days of receiving the piece) and give them a chance to resolve.
Had you done this 1.5 years ago and the dealer not resolve, only then would I consider the dealer a dirty player.
Had you done this 1.5 years ago and the dealer not resolve, only then would I consider the dealer a dirty player.