The post said the woman spotted a rat running around near her feet at Fat's Asian Bistro and notified the staff.
The woman believed she would be speaking to a manager, but instead was handed a receipt by her server with $30.95 knocked off the bill for "SEEN RAT."
Kevin Fat, chief operating officer of Fat's Restaurant Group, said the incident was highly unusual -- as was the note on the receipt.
"The manager put it verbatim what the guest saw or stated, that's not normal practice," Fat told KTXL-TV. "In our 14 years in Folsom, we have not experienced something like this before."
Fat said the restaurant manager was attempting to do right by the customer.
"That's something that that manager at the time thought was appropriate, [it's a] learning lesson," Fat said.
He said the eatery's staff acted appropriately and immediately contacted a pest control firm, which could not find any sign of rats in the building.
The Sacramento County Environmental Management Department sent a health inspector, who also didn't find any signs of infestation.
"For example there were no droppings, there were no live or dead bodies, no nesting, no gnawed food packages," the inspector wrote in their report.
The inspector said the customer may have spotted a rat that temporarily sought shelter in the restaurant.
"I think with the weather, it's possible that one came in, maybe the back door, and maybe wandered around the dining room and was chased back out," the inspector said.
Fat said the company is taking the incident seriously and is attempting to contact the customer who had the experience.
