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's 645, ME Super, Spotmatic II
Minoltas SRT 102, SRT 202, Maxxums 7000 and 7000i
Canons A1(X2), EF, TX, FT QL, EOS 630
many Nikons-black F2 eye level, chrome F2AS N90s, F4E, N2000, N6000, N6006, Nikomat FTN, N5005