Moving worksheets into viewing area

I need help finding a worksheet when it has accidentally been moved out of
the viewing area. In the past, I've selected all with ctrl-a, copied the
selection, and then pasted to a new sheet. I know the sheet is open because
I can see the individual cell formulas above and below the viewing area as I
move around the sheet with arrows. Is there a keyboard command I can use to
try and move the original sheet back into the viewing area? I've had 2
computer-illiterate coworkers do this now, and I can't figure out how they
are making these sheets disappear, much less get them back. Thanks in
advance.