Okay. "I have no option to overwrite" was not mentioned in your original post. Can you save it under a different name, at least temporarily, so you don't lose your work? Then the usual first thing to try is to quit then restart Numbers. If not that then reboot. When it comes to glitches/bugs, the solution often comes down to trial and error until something works.
Is this not the message you see or is this the message but the "replace" button does not work?

Did you navigate to the location listed in the message yourself using Finder? I ask only to clarify if by "I do a search" you meant you used Spotlight or Finder's search bar or if you searched by hand. English is not a precise language; the same word can mean different things and different words can mean the same thing.
I am kinda wondering what happened to the first one you saved. I am hopeful rebooting your computer (which will reboot Finder) will make it appear.