You'll have to evolve it eventually if you want to get his PL Data in the Gallery. Yeah, Gyro Ball sucks, I ended up giving him Scolipede, Galvantula, Empoleon, and later a Scizor. I might give him a Volcarona as well. Probably more than needed, but oh well.
And no, there's no item that prevents evolution, but you could always just say no when it starts to happen.
To err is human. To blame your computer for your mistakes is even more human.
personally, I tend to keep both the evolved and unevolved forms of their Best Link (basically, anything that can be displayed alongside the character's portrait). Yeah, you need to evolve a Forretress if you want to complete his gallery information, but there's nothing saying you can't still keep a Pineco around for him as well.
Galvantula also has that same move.
I really think it should've gotten Signal Beam, though. The variety between Electric-types is terrible.