Does the company provide travel leave?

Travel organized by the company is usually for all employees and takes advantage of weekends. Your colleague is obviously using his own vacation.

It is the company's decision to let you take over the job, not him. If he is not here, it does not necessarily matter whether no one does it or you do it or others do it, and it has nothing to do with what leave he takes.

What he said may not necessarily be true. It’s not annual leave, it’s not paid leave. Is it still sick leave to go out for fun? In this case, a warning letter will be issued.