Once I've rejected the survey readings, can I get them back?
Yes, the readings remain within the database labelled as rejected. You can approve them at a later time.
I click on the tool tab but can't see any tool data.
You might not have approved data for that tool for that Drillhole. Click on Surveys under the Approve menu (in the left-hand menu area) to see which Drillholes have what data.