Helicopter searching the sky for something.

Was outside with my girlfriend in northwest Las Vegas when we heard a helicopter approach. As it was directly overhead, we both noticed its spotlight was aimed up as it proceeded to scan the clouds with its light. A few minutes passed as we watched the helicopter appearing to search for something in the sky near the mountains northwest of the city.  Then we saw the helicopter move its spotlight towards the ground and it flew out of sight.  For the next 30 minutes we heard helicopters flying overhead, but saw no lights at all.  I am just reporting it here in case anyone else saw anything strange.