If you choose to drive it with the friction material missing from the inboard pad as you describe it, you will have steel, not friction material, rubbing on the rotor. Consequently, you will have only half of the braking power on that one wheel. While you apparently have it all apart, just compress the caliper piston and install a new set of pads for that wheel. Why wait till Monday? Then you should replace the brakes on the other wheel too because you are paying for a complete set anyway. Those pads may be defective or rusted to fall apart like that before they're worn out. That would be the smart thing to do. Be safe.
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