While using Gnumeric, enter data into a cell, but before pressing return or
otherwise exiting the cell, press F7 to do a search (this is common
behavior when, for example, entering grades and searching for the name of
the next student, which is where I encountered this bug)

Intuitively, the user thinks of this in the same way as moving to another
cell.  Implicitly, the data that he/she typed into that cell should now be
present in the cell where it was typed, and the focused cell should now be
the cell containing the searched-for term.  Instead, Gnumeric inexplicably
does nothing with the data which had been entered but not "committed" by
pressing return/tab/arrow key.  If you now return to the cell where you had
typed your data, you will find a blank cell.

This behavior differs from that in Microsoft Excel and Open Office, and is
very hard to justify.  After all, if the user types data into the cell,
they presumably have a reason, and are capable of deleting it themselves if
they so desire.  On the other hand, it's quite easy to forget to move out
of the cell before searching for the name of the next student while
entering grades, and thereby lose the last grade you entered.