If it ended up getting an alkaline battery in there, it may be frozen by a corroding battery. A dead alkaline is a leaky battery. I've seen that more than once on K-1000's.
I sure hope not. But I think the reserve battery is still good. When you remove the AA pack and reinstall it, the settings stay the same. I just want to replace the reserve battery because I've had the camera 2 years and don't know how long it's been in there.
Pentax 645, Pentax 6X7MLU, and many Nikons-F2 Photomic F2AS FM2N N2000 N6000 N6006 Nikomat FTN