Dez Bryant -- Diamond Finder Is Unemployed Volunteer

Imagine you're out of work and looking for a paycheck ... and then you stumble upon a HUGE DIAMOND EARRING -- would you give it back???

Lucky for Dez Bryant, the man who found HIS diamond after it fell out during a Dallas Cowboys practice yesterday isn't you.

The guy with the golden heart is Miguel Preciado ... who's been volunteering at the Cowboys practice facility in Oxnard, CA while looking for a permanent job.

Preciado tells us ... he NEVER (not even for a second) considered keeping the diamond and selling it ... even though hawking it could've brought in THOUSANDS of dollars.

"I'm just a volunteer who did the right thing that I would have wanted done for me," Miguel tells us.

When Miguel gave the diamond to #88 -- Bryant insinuated he'd be hooking up Miguel with some sort of a reward, but Miguel says the move was never about money -- he just wanted to do what's right.