Jokes on them, I keep a bunch of old screws, nails, etc. They come in handy. I'd disturb those containers and mix in part the box of paperclips I already have. Then dump the others around the house randomly.

Then, tilt my fridge and hide the correct one under it, in the little lip formed by where the metal is rolled.

Unless they actually lift the fridge and turn it almost upside down, that damn thing isn't coming out of that lip.

By the time they've gone through all of the fake hiding spots and determined that all of the other clips are the wrong ones, a big portion of the time is gone (and I'm assuming the clip somehow identifiable and that they have a way of doing so, otherwise they're screwed from the beginning)

Nobody with sense is going to turn the fridge over to check under it unless they've exhausted other places.

It's all about wasting their time and making use of human habits, not necessarily a super secret spot.

But, that spot rules out metal detectors, and won't have visible signs of recent movement (because I keep the kitchen absurdly clean, there's no built up dust or grime under it to show the movement). If I hadn't had to turn the fridge on its side to get under they're for some repairs, I wouldn't know the lip existed in the first place. So the chances of any of the investigators and/or subcontractors also knowing that a decades old model of refrigerator happens to have a rolled metal lip is pretty damn low.

They'd do the human thing of looking under it, or even lifting it off the feet and checking under those, but not look further because any of the other places under there would allow a little piece of metal to fall out freely when their first search happened.

But, there's a similar spot on the interior of our washing machine that I found when replacing a switch. Same kind of deal, but the area where the washer is isn't as clean, so it would be obvious enough.