Help With Missing Lock

Hey Nick. It's unfortunately a bit difficult to say what lock you need without seeing the original. It doesn't look like yours mounted to the outer frame, since there are no mounting holes above or below the hole for the lock. Therefore I want you to start by looking at our 82-244. I'm wondering if it mounts to those two protrusions within the door. Look over the dimensions and see if you think this might work for you. I can't be certain without seeing the original, but this is what I feel best about for now. 

The old handle set should work fine with a new lock, so long as the thumb lever is not damaged. Let me know if you have further questions. You'd simply remove the handle set when installing the new lock, then install the old thumb lever and handle set back on. 

Looking at your photos, I believe you might need the 82-244 mortise lock since you have those screw bosses inside the patio door. Check the measurements of the 82-244 along with the mounting screw locations.