Is there a way to refer to a Pivot Table's total cell?

When a pivot table is created, there is a “total” at the bottom of the table.
However, since the pivot table might be dynamic (i.e. number of rows can change if you change the underlying data), if you refer to that cell by it’s absolute position (e.g. “'Sheet1.B33”), things might break if the pivot table changes the number of rows.

Is it possible to reference this cell in a way that does not break if the pivot table changes?

Yes, use the function GETPIVOTDATA. See help, or from older OOo guide, or in German, or section ‘Using Pivot Table results elsewhere’ in the Calc user guide chapter 8.