Here’s more info from another article. I still have no idea why they went to Taco Bell:
On Jan. 26 at 5:01 p.m. local time, police dispatchers in Ocala, Florida, received a call from a woman who reported that she and her boyfriend had found a grenade while fishing in the nearby Ocklawaha River.
But her story didn’t end there. After examining the grenade, the woman’s boyfriend placed it in the trunk of her car, and the pair drove to the Ocala Taco Bell, where they notified the police, Ocala Police Department (OPD) representatives posted on Facebook.
The couple — Lorena Upton and Charles Carter — were magnet fishing in the river, searching for valuable metal scraps that they could salvage and sell, Officer Jameson Boucher recorded in a case narrative. When Carter fished up the grenade, he put it in a bucket along with the other bits of scrap metal, stowed the bucket in Upton’s trunk, and then drove with Upton to a Taco Bell to make the phone call to the police, Boucher said.
I have never heard of “magnet fishing”. I suppose you could do it out of curiosity just to see what you might find, but using just a magnet will only bring up iron or steel and miss more valuable copper or aluminum, Does not make much sense money wise.