Lil Scrappy -- My Arrest Was a Big Mistake

Lil Scrappy is STILL behind bars following his arrest in ATL yesterday ... and it's all because he failed to check in with his probation officer ... TMZ has learned.

We broke the story, Scrappy was locked up in Georgia yesterday for violating his probation stemming from a 2008 marijuana possession case.

But nearly 2 weeks before he was arrested, Scrappy filed documents with the DeKalb County Superior Court, begging the judge to recall the warrant for his arrest.

In the docs, Scrappy admits he failed to check in with his probation officer on August 9, 2012 ... but says it was an honest mistake because he had been on non-reporting status for 1.5 years and didn't know a check-in date had been scheduled.

Scrappy insists he has otherwise been a model probationer and wants his arrest warrant recalled ASAP.

The judge hadn't ruled on Scrappy's request by the time the rapper had a run-in with police yesterday, which is why he was arrested and taken to jail.

Scrappy is expected to go in front of a judge sometime in the near future ... but for now, he remains behind bars.