3:21 PM PT -- Seems Luke Bryan's fall wasn't caused by a fan's phone ... a new angle shows he just sorta slips onstage and happens to land on top of the cell. Might want to look into non-slip shoes, Luke!

Luke Bryan's proving the show must go on ... 'cause he slipped during last night's performance and crashed to the ground hard -- but, took the incident in stride.

The country music singer-songwriter performed at the Coast City Country Festival in Vancouver last night ... and while hyping up his next song Bryan stepped in the wrong spot and went flying into the air.

Check out the clip ... Bryan looks like a cartoon stepping on a banana peel, really getting some height on his slip -- and, revealing he actually stepped on someone's phone.

LB could've gotten seriously hurt, but he pops up pretty quickly and laughs it off ... before asking if anyone had captured the insane moment.

Of course, pretty much everyone in the front row had cameras trained on Bryan ... and, he borrowed a fan's phone to show a clip of his fall on the big screen for the entire stadium to enjoy.

Anyhoo ... Luke and the crowd laughed about the incident and moved on -- and, Bryan probably handled it so well because it's not the first time he's eaten it during a performance.

Remember ... TMZ obtained video back in 2014 of Luke rockin' out at a concert in North Carolina before stepping too far forward -- and, literally face-planting offstage. People rushed over to help him back then, and he got a few stitches, but ultimately he was fine.

And, there's this from 2022 ... where Bryan showed off some booty-poppin' dance moves -- when his ankle gave out and left him fully on his back.

BTW ... Bryan's got a show Wednesday in Saskatchewan, Canada -- watch your step, Luke!!!