YoungBoy had a scheduled appearance at The Moon nightclub in Tallahassee, but there's no evidence he ever showed.

Law enforcement sources tell us cops came in contact with YoungBoy on his tour bus-- we don't know why -- and when they ran the rapper's record, they discovered he was a fugitive from Georgia for allegedly committing assault, weapons violations and kidnapping.

The 18-year-old rapper has had lots of legal trouble ... he wrecked a Lambo, among other things. He was also arrested for a case connected to a series of shootings in Baton Rouge, LA back in 2016. He was also accused of firing a weapon during a drive-by shooting.