Weeks later , Thompson and Acosta returned to Las Vegas to report for Rolling Stone on the National District Attorneys Association 's Conference on Narcotics and Dangerous Drugs being held from the 25th to the 29th of April 1971 , and to add material to the larger Fear and Loathing narrative . Weeks later , Thompson and Acosta returned to Las Vegas to report for Rolling Stone on the National District Attorneys Association 's Conference on Narcotics and Dangerous Drugs being held from 25 â `` 29 April 1971 , and to add material to the larger Fear and Loathing narrative .