If the PM has done her job, the project would be functioning with a high performing team working under well defined roles, high performing processes, a clear direction and a good degree of buy-in with all stakeholders.
Ideally, the PM should be able to leave for a period of time and return with little to no adverse effect.
**Before goes:** When handing over the reigns for a vacation, current high priority risks and exceptions should be briefed to the temporary PM with clear direction on his tasks to be accomplished during that period.
**When returning:** Upon return, a counter briefing describing progress against those tasks and where the project is in terms of those risks and exceptions are required. Everything else ought to be running like a well oiled machine.