my thoughts (and I'm not an expert) would be something along the lines of 1) pressure washing (with perhaps an odor eliminating additive) 2) leaving the door open to air out; and 3) putting large pans of baking soda out for a while to absorb odors.

If it were my house, I would be looking at cutting out and replacing the lower 2-3 feet of sheetrock, then cleaning and sealing the concrete floor.

The alcohol-based white shellac used for smoke damage will seal the drywall
http://www.homedepot.com/p/Zinsser-B-I-N-1-Gal-Shellac-Based-White-Primer-Sealer-182406/202016525

Kilz makes some low VOC and low-odor primers for pet stains and odor blocking ... http://www.kilz.com

Get a power scrubber and scrub the heck out of the concrete floor with TSP or a low-sudsing laundry detergent with OxyClean or a bleach, rinse, and let it dry with the garage door open for a while ... air is your friend.

Then, if needed, hit it with one of the kennel cleaner/deodorizers - ask a vet

Sealing the concrete with an epoxy floor finish made for garages might be needed.