As noted, Tuesday's WWE Backstage viewership was not available on Wednesday because the show actually aired on Wednesday this week, at 12am ET on FS1 instead of the usual timeslot of 11pm ET.
The timeslot change this week was due to the return of NASCAR programming to FS1. There was speculation on a permanent timeslot change after FS1 then announced that next week's Backstage episode will also air at 12am. NASCAR will run from 8pm until 10pm on Tuesday, while "A Future WWE: The FCW Story" will run from 10pm until 12am
It looks like WWE Backstage will return to the 11pm timeslot on Tuesday, June 2. TV Guide currently has Backstage listed for that normal timeslot on June 2. There's no word yet on if classic WWE programming will air that Tuesday, as "To Be Announced" is currently listed from 7pm until 11pm.
You can see the confirmed timeslot change for next week below: