From CNN’s Abbie Boudreau and Scott Zamost

NEW ORLEANS, Louisiana (CNN) — As Hurricane Gustav took direct aim at New Orleans, social workers and homeless advocates spent the last few hours before the evacuation deadline looking for the homeless.

Early Sunday morning, Mike Miller from the group Unity of Greater New Orleans was clambering into abandoned buildings, looking for signs people had been sheltering there.

“Watch out for the nails,” he warns as he steps inside.

Miller says that there are more than 71,000 abandoned and blighted buildings in New Orleans and many have become shelters for the city’s homeless. He says that since the homeless don’t have TV, radio or newspaper subscriptions, word of mouth is the only way to warn of the imminent storm.

“How do you find those people, how many of those people will be missed? Miller asks. “Is that the kind of thing you can only count after a body toll?”

In building after building, Miller shouts inside, but gets no answer.

Under a bridge, he finds one homeless man and warns him that the last bus will soon be leaving the city.

“I’ll be there,” the homeless man promises.

“Beautiful,” Miller responds.

In a nearby park Miller is cheered to see only five people, instead of the 35 who were three two nights before.

Among the five is a man who goes by the name Guitar Mike. He says that he doesn’t plan to leave.

“There ain’t no water coming,” he insists. “It’s not going to happen.”

“I went through Katrina, and I survived that one,” Guitar Mike says. “And if it does happen, I will survive this one.”

The exchange is frustrating for Miller, who all night has been offering to drive people to the bus station himself.

A few minutes later, Miller finally finds a taker, a man who has just gotten out of jail after being caught sleeping in an abandoned house.

“Get on that bus,” Miller tells him.