keep something warm for someone
keep (one's) (something) warm
To occupy a position for or take over the responsibility of someone else while they are absent. Usually used in the form "keep (one's) seat warm," and often followed by "for (one)." I'm don't usually work in reception; I'm just keep Mary's seat warm while she's on sick leave. Bob asked me to keep his place warm while he's on vacation, so, if you have any questions, you can direct them to me.