Prince Harry appeared to be mistaken for his older brother, Prince William, on Friday during a charity event near his home in California.
The Duke of Sussex attended the annual One805Live! concert at Kevin Costner's oceanside estate in California last week, unaccompanied by his wife, Meghan Markle, who was reportedly unwell.
During the event, the father-of-two presented an award to local pilot Loren Courtney - and joked that they both felt more comfortable flying helicopters than onstage.
Stars such as Rob Lowe, Jeff Bridges and Pink attended the event to celebrate the heroism of Santa Barbara’s first responders while Richard Marx was one of the musicians to perform.
After performing at the charity gig, the American singer chatted briefly with the prince, which Richard's wife Daisy Fuentes caught on camera before posting the exchange between the two on social media, for her 324,000 followers.
Daisy - who is a model, comedian and former MTV host - then posted a picture of the two, engrossed in conversation. However, she mistakenly tagged The Prince and Princess of Wales's Instagram account.
Prince Harry (pictured right) appeared to be mistaken for his older brother, Prince William, on Friday during a charity event near his home in California. Harry chatted to American singer Richard Marx (left)
Quickly correcting the error, Daisy then tagged the Instagram account 'Prince Harry of England', which is run by a royal fan and boasts 410,000 followers.
Prince Harry has only ever publicly used Instagram via the former 'Kensington Palace' account - which has since rebranded to the Prince and Princess of Wales' official channel - and SussexRoyal, which has been inactive since the Duke and Duchess of Sussex stepped back as working royals in 2020.
The faux pas was the second made by Richard and Daisy, as the singer nearly failed to recognise the prince entirely when he first walked past him.
After finishing his set, the American singer came off stage but almost missed Prince Harry, who was waiting to congratulate him on his performance.
Capturing the moment, Richard's wife, Daisy, filmed the awkward encounter between the oblivious singer and the prince.
As heard in the clip, the pop-singer was quickly alerted by backstage staff to the prince, who had initially gone unnoticed.
Notifying the performer, they swiftly prompted 'Richard, Prince Harry' as they gestured to the duke. Before the clip cuts out, the royal is heard saying: 'Hey! Well done.'
The Duke of Sussex attended the annual One805Live! concert at Costner's oceanside estate in California last week, unaccompanied by his wife who was reportedly unwell
Pictured: Prince Harry shaking hands with Richard Marx, who performed at Kevin Costner's One805Live! concert yesterday
Harry is seen here with the head of the World Health Organization Dr. Tedros Adhanom Ghebreyesus, along with actor Forest Whitaker and Queen Mathilde of Belgium
Meghan joined Prince Harry at the charity event last year and guests had hoped the Duchess would be in attendance again. However, a source told the Mirror: 'The word is that she is sick and could not make it'.
Over the weekend, the prince attended a dinner organised by World Health Organization (WHO) in New York, his wife Meghan still absent from public appearances.
Present, however, was Queen Mathilde of Belgium, actor Forest Whitaker, several UN Agency Heads, and other dignitaries, for an event to honour survivors of childhood violence.
All are in New York for the UN General Assembly, which is set to kick off Monday morning in Manhattan.
Officials from countries like Sweden, Colombia, Zimbabwe, Georgia, Canada, Iceland, and Brazil were also present.
Prince Harry is seen greeting Queen Mathilde of Belgium during a high-level dinner on 'Violence against children and its impact on mental health' in New York City
Also in attendance were high-profile figures like Whitaker and Shudu Musida, who, along with the survivors, helped pen an open letter last week demanding urgent action from world leaders to end violence against children.
This comes ahead of the first-ever Global Ministerial Conference on Ending Violence Against Children, which is set to take place in Colombia in November.
Signatories of the letter included Harry, Mathilde, and Belgian Prime Minister Alexander De Croo, who was seen conversing with the Duke of Sussex and actor at length during the event.