Lost keys

I almost never lose my keys.  I always put them in the same place: they move between my mantelpiece and my pocket.  And as such, it is rather disturbing to me when, as happened on Saturday, something goes awry.  I am 99% certain that the keys are in the house: I had them when I drove up in my car, and couldn't find them the next time I went to leave the house.
I have no idea where they could be, where I could have put them.
Yours, very distressed by the disturbance in the space time continuum,
N.