Let's look at this as a hypothetical. If Steven were a female that went missing.
- Le would look at who she knew
-who was in the area that was acquainted with her
-and did they change their routine in any way.
-who had one of the last contacts with her
GW fits all four of the criteria.
If GW got back to St George in time for the noon meeting (11am PST), he was in St George an hour before the figure was seen walking on the video. Easily verifiable by LE, if need be.
ETA: I've put GW's arrival in St George (per KCN's statement here on WS) on the timeline, in the appropriate place...sourced to "GW himself". It's a good reference and documentation of the statement.