You had it...I mean, you opened the box to fondle it and look through it, right? It's there somewhere, just find it.
Ned, let’s infer some things and figure out where the scope is in the house.
Assumptions:
The scope was known to not have an immediate use.
As a fragile item, it’s still in the original box even if handled a couple times.
It was placed somewhere out of the way of more frequently accessed things, so it wouldn’t be in their way, and didn’t risk getting dropped or unnecessarily moved.
Gun related things are typically kept in one area of the house.
The OP has a lot of cabinets and drawers as he’s made a point of how the house has been searched.
It’s likely that if a gun was on order, the OP buys quite a bit of supplies.
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Deductions based on those assumptions:
It’s behind newer supplies;
It’s in a place that is not well lit;
It’s in a place that is physically uncomfortable to fully explore, such as a low or high cabinet, which would also keep it out of the way.
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Alternatively, if you don’t keep a tidy area, and if this scope was not a purchase that you consider especially valuable, you combined it into a box with other long term supplies like powder and bullets, maybe for this gun, maybe by the box this gun’s stock came with, or back to the untidy theory, it’s on a workbench under paper or similar unimportant cover.
Question, where is the base and rings for this project? If you don’t have them yet, could you have already put this scope on a different rifle, and forgotten? If you do have them, they will probably be with 10 feet of the scope.