The bike was taken Wednesday when its owner, John Phillips, dropped off some items at his mother-in-law's home in Pittsburg.
Phillips left it in the driveway and when he came back out it was gone.
He does not have a driver's license because of the disease and the bicycle is his only mode of transportation.
John's wife Carmel pleaded to whoever took it, "Bring it back, let him be out in the world as long as he can. Alzheimer's is an absolutely atrocious disease that will take everything from both of us very swiftly and give him the time he deserves to do the things he wants to be and be autonomous."
Whoever took the bike might not get very far because it needs a custom charger.