CHICAGO (CBS) – Are you counting on using all those airline miles you’ve racked up on credit cards to keep down the cost of a vacation? Maybe not.

CBS 2 Investigator Pam Zekman reports on what experts say is the latest twist in identity theft scams – thieves who’ve found ways to steal your miles. You might not find out until you try to use them.

Flying is such a hassle these days, the only bright spot is using up all those travel miles on a dream vacation.

Unfortunately, the dream turned bad for one local couple.

“I was very upset, and I’m still upset,” Michael Hynes said.

He and his wife thought they had racked up 175,000 miles, but United Airlines told them they only had 12,000. United said the rest of the miles had been spent on hotels in Singapore.

“I said ‘Okay, did I have fun?’ And she, the girl goes ‘I don’t know, did you?’ And I said, ‘No, it wasn’t me,’” Hynes said. “She said, ‘Well, there’s nothing we can do about it.’”

Membership numbers, passwords and a security question must be answered to access an account, so Katherine Hynes wondered “how was someone able to use our points and steal them like this?”

Katherine and Michael made countless calls to get their points back, only to be left frustrated.

“Totally. Off the wall,” Michael Hynes said.

Katherine said, after the 2 Investigators got involved, “They suddenly called and said ‘Okay, here’s your points back.’ That really is wonderful.”

But she said they still wonder “how they were stolen. … They closed the case, without giving us any answers.”

So how does it happen? CBS 2’s investigation found there are many different ways for cyber crooks to steal your miles.

Tim Armstrong, a computer security expert at Kaspersky Lab, said some victims will get an email with a trip confirmation or a special offer, asking them to enter their frequent flyer information.

“A sense of urgency is important, and that’ll make people log in to those sites and give up their details,” Armstrong said. “They can use these schemes to collect people’s miles, to buy tickets, and then resell those tickets to third parties. And they’ll collect money that way.”

Also, watch your boarding passes. They can have enough details for crooks to hack into a system and steal your miles.

Federal Trade Commission regional director Steve Baker said, “Consumers probably ought to be taking those home with them, and disposing of them properly, instead of just throwing them in the trash bin at O’Hare.”

A United spokesman said there have been other complaints about stolen miles, but he declined to say how many.

He said it is the consumer’s responsibility to protect their passwords. However, when a fraud claim is validated, United will reinstitute the miles, or provide compensation when necessary.