Walker raised his boot dangerously to challenge Gabriel during Arsenal's defeat at City.
The incident happened just moments before half-time, but Arsenal's animated appeals for a penalty were swiftly waved away by the referee.
Walker's foot was head high as he attempted to challenge Gabriel from a corner and came close to making contact with the Arsenal man.
And Arteta was incensed at full-time after VAR appeared to opt against reviewing the incident.
"That has to be checked [by VAR]," Arteta said after the 1-0 loss.
"They said that they checked, and I asked 'How the hell have you checked if you took two seconds to check that action?!'
"Obviously there is something there."
After being told that Sky Sports understood VAR chose not to look back at it, he added: "Yes, I think that's what happened."