"There is a fly in the room." You see no fly hence Absence of evidence is not evidence of absence"
That example falls short. Not seeing a fly is not the same as not seeing an elephant. What size is the room? Is there something big enough to hide an elephant or fly? What methods were used to look?
There are some exceptions, to be sure, but in your examples it is 100% reasonable to find the evidence if one is willing to look. Also, we know what flies and elephants are, their properties, etc., and how to detect them. In the case of god, anytime someone has been able to loosely define what we are looking for, then absence of evidence absolutely is evidence of absence.