Bicycle detail

My friend and I locked 2 bikes with 1 cable lock on the bike rack in front of REI. We went into REI to buy U locks. We decided to buy the lock online because we could get a better price. We exited REI and both bikes were still there. We left the bikes locked at REI and went directly across the street to eat at Nando's. I positioned myself so I could watch the bikes while we ate. 15 minutes went by with me watching carefully, but then I realized one of the bikes was gone. Somehow they cut the cable and stole 1 bike while I was watching, I must have been looking down. They left the cut cable lock and the 2nd bike. I went into REI and informed management and asked if they had a camera and they said no. I also asked Nando's management and they said they couldn't help. We just bought this bike used from EVO bike store in Rockville about 2 weeks ago.