There is no need to mail another return with those words on it. The IRS will figure out that the return you already mailed is your "real return".
You can't track a mailed return until the IRS starts processing. They haven't processed mailed returns for many weeks. Yours is likely sitting unopened along with the millions of other mailed returns that haven't been opened. The IRS has promised to get to them in the order they were received.
See this info about the current status of IRS operations:
https://www.irs.gov/newsroom/irs-operations-during-covid-19-mission-critical-functions-continue
