Colin Kaepernick -- CHAOS AT COSTCO ... QB Makes 1st Public Appearance Since Investigation

"Attention Costco shoppers ... right now, we're having a great deal on a 24 gallon bucket of toothpaste ... and OH MY GOD IT'S COLIN KAEPERNICK!!!!!!"

For the first time since he was listed as a "suspect" in a sexual assault investigation, the 49ers QB made a public appearance yesterday ... signing autographs at a S.F. area Costco.

The appearance was a promotion for MusclePharm -- the supplement company that vowed to stick by Colin's side throughout the investigation.

Unclear if Colin addressed the investigation during the appearance, but he definitely signed a ton of autographs for fans ... many of whom tweeted about the situation ... in between stocking up on ungodly amounts of shampoo and band-aids.