Anne Troy provided the workaround, here is the explanation of what you
observed.
Reformatting does not change the underlying value, only the display. In
particular, changing the format from text to numeric does not change the
value in the cell from text to numeric (as you discovered), it merely
prepares the cell to receive the next input a number. Pressing F2
simply puts you in edit mode (you could click on the formula bar with
the same effect); it is pressing enter after getting into edit mode that
reenters the data, so that it is reinterpreted as text.
Jerry