The shrinked mode for entering cell references in the solver dialog can be
cancelled by using the ESC key. In this case Calc is supposed to restore the
value present before the dialog was shrinked. But: It does not.

Try this:

(1) Open the Solver dialog (Tools - Solver...)

(2) Set the cursor into the "Target Cell" field or any other field for wich
shrinked mode is possible.

(3) Click to the spreadsheet in the background, for example click cell A1. The
cell reference $A$1 will be shown in the "Target Cell" field.

(4) Click the Shrink button to turn the Solver Dialog into shrinked mode.

(5) Click to the spreadsheet in the background. Click to a different cell than
before, for example click cell A2. The cell reference $A$2 will be shown in the
text field of the shrinked dialog.

(6) Hit the ESC key. This maximizes the dialog again.

Note that this procedure leaves $A$2 in the "Target Cell" field, which is the
latest reference selected, whereas it should have restored $A$1, which is the
entry present before shrinking.

According to the Spec. http://specs.openoffice.org/calc/features/Solver.odt
paragraph 1.3.1.2 Calc is supposed to restore the old value.