It's a bit like when you "...can't see the wood for the trees...": You are looking so hard for something that you miss what it is you are looking for.
A couple of days ago I was looking for my reading glasses. I had been sitting at my desk but I was convinced I had put them down in another room. I had a quick look around the room, then went round the house hunting for them. (btw I have a lot of 'stuff' in my house). Finally, armed with another (slightly broken) pair, I returned to my desk, sat down, then realised that my 'lost' glasses were in fact, sitting right in front of me, next to my computer.
Why had I not seen them straight away? I 'couldn't see for looking'...🤨