Mercedes F1 Team boss Toto Wolff has admitted Lewis Hamilton and his engineers did not tell him about a secret motorbike test at Jerez in December.
The five time world champion even crashed as he tested the plain black Yamaha superbike according to the report on motorsport website ThisIsF1.
Wolff said: "We had a laugh because I couldn't get hold of him and couldn't get hold of my chief strategist and one of the race engineers.
"I found out they were racing motorbikes in Jerez and nobody would pick up the phone. And then they were a bit apologetic."
Wolff added that Hamilton's extra-curricular activities are often "worrying", but understands that the 34-year-old world champion needs to do "what works for him".
"Every time he's able to decompress from motor racing, he comes back stronger," he said. "We mustn't be judgemental. Some people go on a meditation seminar to India. Others do skydiving."
Hamilton told France's Auto Hebdo that his next ambition is to test a MotoGP bike.
"I'm going to ride one, that's for sure," he enthused during an interview at the Melbourne grand prix. "I just need to ride more. It's a dream I want to realise.
"I watch all the races. Even when I'm on a grand prix weekend, I quickly leave my briefings to find a screen," added Hamilton.