MINNEAPOLIS — Joey Prusak was appalled when he saw a customer at the suburban Minneapolis Dairy Queen store where he works pick up someone else’s $20 bill and slip it into her purse.

So when the woman got up to the counter to order, Prusak refused to serve her unless she returned the money. When the woman refused, the 19-year-old store manager went a step further: He gave the visually impaired customer who hadn’t realized he’d dropped the money $20 out of his own pocket.

“I was just doing what I thought was right,” Prusak said Thursday as he recalled the incident from earlier this month. “I did it without even really thinking about it. … Ninety-nine out of 100 people would’ve done the same thing as me.”

Even so, Prusak has received loads of praise since a customer’s email about him to Dairy Queen was posted online.

Now, people are calling the store, thanking Prusak and even offering him jobs. Customer traffic at the Hopkins Dairy Queen has doubled, and many people are leaving large tips — money that Prusak says he will donate to charity.

Prusak said he even got a call Thursday from billionaire Warren Buffett, whose company owns Dairy Queen. “He called and thanked me for being a role model for all the other employees and people in general,” Prusak said.

Prusak has worked at the Hopkins Dairy Queen since he was 14. He’s trying to save money to go to school for business management and has managed the store since the spring.

The visually impaired customer who dropped the money during the Sept. 10 lunch rush was a regular. Prusak said he thought the woman who picked up the $20 bill would return it. Instead, she looked at the man, then put the cash in her purse.

“I was appalled,” Prusak said. “I didn’t know what to do or say.”

Prusak thought for a moment, and when the woman approached the window, he asked her to return the money. But she claimed it was hers. The conversation went back and forth. Finally, Prusak recalled, he told the woman: “Please return the $20 or get out of the store, because I’m not going to serve someone as disrespectful as you.”

Prusak said the woman stormed out, and he served the other customers. He then went over to the man eating his sundae and gave him $20. Prusak didn’t tell anyone about it, other than the other employee in the store.

But another customer saw the incident and sent an email to Dairy Queen. The email was forwarded to store owner Dave Pettit, who posted it at the store. Another employee took a picture, which has been circulating online.

Dean Peters, a spokesman for International Dairy Queen, said the company is figuring out how to reward Prusak.

Prusak said when he saw what happened, he just couldn’t keep quiet.

“I was going to say something no matter what,” he said. “If she would have returned the money, then I would have served her.”