Ma’s empire is seeing a Chinese regulatory clampdown and made a lot of the government rather cross after he blasted China's regulatory system. That move resulted in the suspension of a $37 billion IPO of Alibaba's Ant Group fintech arm and is widely seen as a bad move.
Of course, if it resulted in him being made to disappear, it would be seen as a particularly terrible move which would put the fear of Mao in the hearts of many Chinese entrepreneurs.
An Alibaba spokeswoman told Reuters that the change was due to a scheduling conflict, declining further comment.
However, news coverage of Ma's absence from public view triggered speculation on Twitter, which is blocked in China, it was not a significant trending topic on social media in mainland China, where sensitive topics are subject to censorship.
To be fair though, Ma is unlikely to have been vanished by the Chinese government for saying nasty things about them. He is a little too high profile for anyone to believe that they would get away with it.