Police are searching for former Vine star Nash Grier‘s mother-in-law, Nikki Giavasis, after she was reported missing earlier this week … TMZ has learned.

Nash’s wife, Taylor Giavasis, tells us her mom Nikki was last seen at the Westin Hotel in Fort Lauderdale on Monday, August 18. Taylor says Nikki had planned to stay in Florida for a month — even booking an Airbnb — but she suddenly went dark.

According to Taylor, Nikki told her she’d call in the morning before heading over to the Airbnb, but that call never came. At first, Taylor says her mom’s phone rang, but no one answered … and soon after, it was shut off.

The Fort Lauderdale Police Department confirms to TMZ … a missing persons report was filed for Nikki on Tuesday, August 19.