Paseo Grill owner Lesley Rawlinson said workers spotted the strange object when they arrived for work Friday morning, KFOR-TV, Oklahoma City, reported Tuesday.
"It says 'In the year of our lord 2012 Creer Pipi claimed this land for azathoth,'" Rawlinson said. "It's kind of a problem that we're stuck with, a very heavy problem."
Azathoth is a fictional deity referred to in myth as well as stories by more recent authors including H.P. Lovecraft.
Police said the monument has not been reported stolen and the owners of the Paseo Grill are responsible for it. Rawlinson said she and her co-owners are hoping the owner of the monument will come forward and claim it.