say an advanced civilization learns how to time travel and walk the multiverse. trying to find us would be hard. the time scale is very small, yes, we occupy a small area, true, but also the scale of life itself may not be discussed much.

there's dozens upon dozens of orders of magnitude of space that a being could occupy. scanning for life through the multiverse and time, it would also be easy to miss us. too small and you see cells and organelles, larger we see organs mixed with bacterial cultures, etc, and at just the right scale we are visible.

there are arguments that earth is a living entity, and there may be larger forms of life going many orders of magnitude larger than planet-sized.

with such a large range of time, location and scale to scan for life, it could be argued we basically don't even exist.