I have the A70 (exact same camera, 1mp less).
Each mode has it's own setting, so if you change automatic to the largest, P mode will remain at 600x800 (or whatever it was already set to).
Your pics are savable but you need a program to retrieve them (and for the life of me I can't remember where to get it). If you don't care about the pics you lost, sometimes formatting (not just "erase all") the card, and resetting the camera to it's original settings will fix your problem.