Bicycle detail

I locked up my bike in front of a very busy Costco in San Francisco. Went in to pick up a prescription, which took about 20 minutes. Cam out and my thick foldy-lock was cut and laying on the ground with my bike helmet that had been locked to my bike. The location was very busy, which to me meant safe. a man that didn't speak english came up to me and using Google Translate on his phone told me a black man walked up, cut the lock and was gone with the bike in less than a minute. No pictures or any other information.