Reading your post was like deja vu for me. I went through this exact same process about my expensive Bernina walking foot a few weeks ago, including the sick worry that it may have been pushed off the table into the waste basket that had gone to the curb the previous day! Forcing myself to breath slowly in and out, I retraced my steps for a third time and finally found it - in the very first place I'd looked. For some reason I had not returned it to the box where it belongs, but I had put it in the drawer next to the box and didn't see it the first or second time I looked there.
I have a sewing table with a recess for the machine, and frequently things fall in on the side by the motor, and sometimes they fall in such a way that they are out of sight underneath the moveable platform that the machine sits on. If you have a hiding place like that, it would be worth checking. It may have fallen during the move and bounced or scooted under furniture anywhere between point A and point B. Another place to look is near the phone or the door because you may have had it in your hand when the phone or doorbell rang. Another idea: maybe it got folded into a quilt you were working on. If so, it will probably fall out and hit your big toe because that's just how things tend to show up after they've been out on a spree. I hope you find it soon!