Imagine leaving your home for a few hours to run some errands. When you get back, you find a hole -- about the size of a doughnut -- cut through your front door. Underneath it, someone has  installed a new doorknob. And when you try your key, it doesn't fit.

That's what happened to Owen Wang last month at the Hotel Astoria. It's a musty old building with a creaky elevator, located next to Chinatown's famous "Dragon Gate" entrance.

Wang,  a retiree and an immigrant who speaks limited English, says he pays $300  a month to live here. His attorney, Alex Lemieux, explains that the hotel's new management changed the locks on Wang and at least one other full-time resident and threatened others with notices on their doors, written in English only.

"It just says, come to the front desk and bring us your lease or we're going to change the locks, more or less," Lemieux says. "It' s not a valid notice."

Lemieux specializes in tenants rights, so he knows all about heavy-handed eviction tactics, but he's never seen anything quite like this.

"I've never seen a situation where they just don't even file the papers, they just change people's locks. That's almost unheard of," he says.

When San Francisco Supervisor Julie Christensen, whose district includes Chinatown, heard about the incident, she rushed to the hotel to investigate.

"It turns out to be very complicated," Christensen explains. "Layers of subleases and owners and property managers.  But we got involved because the residents who live there got caught up in the struggle."

The residents are now back in their homes, while things get sorted out. But this story is just one small example of how jumpy people are these days about Chinatown's future. Here's why:

At the end of last year, the Empress of China shut down. It was the neighborhood's last big banquet hall. Now it's up for sale.

Then there's Craigslist and Airbnb. Rooms once occupied by low-income families have begun coming up for market-rate rent on these websites.

And, this spring there was a dramatic housing battle at 2 Emery Lane, a single-room-occupancy hotel. Mayor Ed Lee had to step in to stop almost two dozen families from being evicted.

Owners cited reasons like tenants hanging laundry outside their windows or hanging Chinese New Year decorations for evictions, explains Cindy Wu, a leader at the Chinatown Community Development Center, a powerful nonprofit organization that stepped in to help the tenants, along with Mayor Ed Lee and Christensen.

"It's way more than a misunderstanding," Wu adds. Chinatown is still a haven for poor Chinese immigrants, and she says that requires leaders to stay vigilant.

"If you have owners that only care about the bottom line, that only care about squeezing as much rent out of buildings as they can, then we're really going to have a problem," she adds.

At the Hotel Astoria, where Owen Wang found his locks changed, James DeVoy, who represents the hotel's longtime owners, insists that's not what's happening here.

"There is no bullying, no questionable means. Anything that is done -- and it's going to be on a case-by-case basis -- would be done in full accordance with the law," he says.

DeVoy admits the lockouts were a mistake. He says the new managers lacked copies of the leases and other paperwork needed to determine who has the right to live in the hotel.

In the meantime, San Francisco's Department of Building Inspection has slapped the Hotel Astoria with a citation. An inspector found the building appears to be operating primarily as a tourist hotel. Its permit says it should be mostly residents, like Owen Wang and his downstairs neighbor, Paris Wang. He hasn't been locked out, but is afraid he will be.

"Every day, I take this one to go out," Wang says, pointing to the backpack he carries whenever he leaves his room.

He opens it to show what's inside.

"This one, this one," he says, laughing nervously as he picks out his wallet, identity papers and other items he can't name in English.

"Charger," he says, finally finding the right word. "Cellphone."

Basically, anything he might need if he finds himself locked out for good.