The crime was filmed at a hairdresser's salon in Retford, Nottinghamshire.
In the footage, which you can see above, the young boy's dad can be seen distracting stylist Kirsty Robinson, 26, as she straightens a client's hair.
Within 30 seconds of being inside the shot, the hooded boy nicks the phone and scarpers. The scam happened in broad daylight during school hours last Friday.
Kirsty said: "They were in and out within 90 seconds. When they left we were talking about them, saying they were dodgy and my client said they were eyeing everything up.
"One of the girls joked, "Let me check they haven't nicked my money". And I turned around to do the same and just gasped, "My phone is gone".
"I couldn't believe somebody could use their child in such a way, what kind of life is that young boy going to lead?"
She added: "They are complete lowlifes and it is truly disgusting that they can go around doing this."
Kirsty, who has worked at the salon for six years, has had thousands of shares of the video of the theft after posting it on Facebook.
Her mother Sharon Tuplin, 52, who has run the salon for six years, added: "It was disgusting what they did. They had came with his son and another lad and while one distracted our junior salon assistant, the youngster goes behind Kirsty and just swipes her phone.
"The man, I can only assume was his dad, was asking about having colour put in his hair while the lad brazenly swipes the phone.
"These idiots need catching and quick, the phone has gone but we don't want it to happen to anybody else."
Anyone with information about the theft can contact police quoting incident 429 of 17 January 2014, or call Crimestoppers anonymously on 0800 555 111.