The 43-year-old's discretion means he won't name the international pop star involved in that incident, but admits to enjoying the fact hotel managers get to meet their fair share of the rich, famous and powerful.
The soul singer James Brown is cited as someone who was particularly memorable.
Mr Gardner said: "He was late coming up after his gig at the Carling Academy and then this big American limo with blacked out windows pulls up.
"He got out with the cape, cane, top hat and sunglasses on in the middle of winter. He said he liked me, the hotel and the Scottish people and told me how excited he was to be here.
"He seemed to be exactly the same onstage as off: a legend."
However, the typical day-to-day challenges of running a hotel are now of slightly less concern to Mr Gardner.
At the start of this year he was promoted from general manager of the Glasgow Hilton to a wider role, looking after a further six hotels – The Caledonian in Edinburgh plus the Hiltons in Belfast and Templepatrick in Northern Ireland, and Manchester, Liverpool and Newcastle.
As area general manager he has responsibility for 1635 rooms and somewhere in the region of 2000 staff.
So far he is relishing the challenge. He said: "There is obviously a bit more travel involved but it has been good fun and interesting.
"I am still very attached to Glasgow as it is a fantastic hotel. I was keen to retain a presence here and the new role has allowed me to keep living in Scotland but spread my wings a little bit.
"So I can share some of the great things we do in Glasgow and widening my experience has allowed me to identify things that we can use to improve on customer experience or efficiencies in all the hotels."
In spite of the difficult economic situation, Mr Gardner is slightly more confident in the prospects for the hotel sector.
He said: "We are cautiously optimistic that we are beginning to get back on track as an industry and within Hilton.
"We look to how we are performing in the market regardless of how the economy is. In Scotland we are optimistic we are doing well and growing market share."
Although he is now in senior management Mr Gardner, who progressed from a part-time role to a trainee manager programme, believes working across various parts of the industry is crucial to really understand what happens in a hotel.
He said: "If you are going to be a success in business you need to know all the aspects of your business.
"The training I had was invaluable. I know how to change a keg, cook a sauce and check people in and out.
"Knowing all the detail is important. The fundamental reason we are here is to provide a great experience for guests.
"If you know all the steps to make that happen then it makes you a little bit better at it."
A £2.4 million overhaul of the ground floor and lifts at the Glasgow hotel has been well received.
He said: "We really listened to what customers wanted so there is more comfortable seating, the bar is opened up and the whole reception is a lot more open.
"In the restaurant we have followed the trend where people are far more educated on food and what they want. So we have created a restaurant which is more representative of what a successful high street would be:simple food, well cooked and excellent service.
"We are also putting in a tea lounge as well as we see that trend for afternoon tea continuing to grow."
The big project for Hilton is the £24m conversion of The Caledonian in Edinburgh to a Waldorf Astoria.
It will be the debut of the luxury brand in Scotland and everything is on course for a late-summer launch.
Along with improvements to the public spaces and rooms the 241-bed hotel is getting a spa, a restaurant backed by Michelin-starred brothers Chris and Jeff Galvin, and a new brasserie.
Mr Gardner is confident the overhaul will be worth it.
He said: "By the beginning of September the grand old lady will be a fantastic hotel and we believe it will be the best in Edinburgh.
"It will be a true international luxury hotel and it is a real coup to get the Michelin-starred Galvin brothers up.
"We understand you have to have points of differentiation between our competitors as it encourages people to come back and continue to use the hotel."
In the run-up to 2014 with the Commonwealth Games and Ryder Cup in Scotland many initiatives have been launched to improve customer service in Scotland.
Mr Gardner is supportive of those schemes and believes there is a good foundation to provide "truly excellent service" in Scotland.
He said: "The fundamentals in hospitality are if you employ nice people the rest will follow.
"We need to make sure we have people who are genuinely interested in looking after guests and making them feel comfortable.
"Our job is to give them the tools to do that in regards to training and experience.
"As a whole Scotland has got everything going for it. We have the people and some fantastic hotels."
Craig Gardner was brought up in Campbeltown, Argyll, and studied chemistry at Edinburgh University.
While in the capital he took a part-time job with Stakis Hotels then decided chemistry was not for him and chose a traineeship with Stakis.
He progressed to deputy manager before moving to the Grosvenor and Bond hotels in Glasgow, followed by various positions in England. When Stakis was sold to Hilton in 1999, he stayed with the company and in 2001 opened the first Hilton in Sweden.
In 2003 it was back to the UK to look after the Hilton in Manchester. The next year he was back in Glasgow as general manager of the main hotel on William Street as well as the Grosvenor and the Strathclyde at Bellshill. He is now area general manager in charge of seven major hotels in Scotland, Northern Ireland and the north of England.
A keen golfer, Mr Gardner lives north of Glasgow with his wife and three children.