If we knew the "somehow" steps we might not have to guess and start
shotgunning<g>
Do you mean an entire workbook or just one worksheet from a workbook?
If the former, check the recycle bin.
Maybe it was just re-named.............maybe you can check recently saved
workbooks.
Do you have a backup copy or did you at one time send it to a friend?
Might still be sitting in your sent items.
If the latter and you have saved the workbook, worksheet is gone.
See above for possible recovery.
Gord Dibben MS Excel MVP