I imagined that this would hold the display values for 2 seconds but it does not, the Sensor Zeroed text just flashes up and then goes back to the original display value.
Somewhere else in your code is something that is clearing the screen or over-writing what was there. The code you show should display text and then that thread will sleep for 2 seconds, and then whatever the next statement is will execute. So you have a second thread or a timer that is also displaying onto the screen and doing the over-writing.