A young fan ran up to greet Lionel Messi as he was getting off Argentina soccer's team bus in Uruguay on Wednesday ... only to get snatched up and dragged away by a security guard.

Messi wasn't havin' none of that ... ordering the security team to run down the kid and bring him back for a quick meet-and-greet.

The boy looked SUPER sad when he got grabbed ... but was all smiles after meeting the FC Barcelona superstar.

In the end, the kid got his shot ... and Messi looked like a total hero (instead of a tax cheat).