Yeah, what a horrible Tuesday!!

Here's the deal ... the 30-year-old former Slam Dunk champ says he got a call Tuesday morning from the Orlando PD saying they found his beloved orange Lambo Urus, a fancy SUV that starts at $220k!

Ross -- the 8th overall pick of the 2012 NBA draft -- was confused because he had dropped it off at the Fields Motorcars of Florida dealership recently to fix a flat tire ... and thought it was safe!

But, cops explained the situation to Ross this way:

"Two guys broke into the dealership, smashed through a glass, went through desks, grabbed keys, go out to the lot and start seeing which key works and the key that they stumbled upon was MY key."

"They take this car and they start driving ... [the cops] find these dudes cruising around like Winter Garden in my whip. They start the chase, the dudes take off IN MY WHIP, smash it, lose control of it and crash it into the side of a building. Completely totaled."

"So, now I'm pretty much without a car ... so now we back to basics. Car shopping. I'm so sick right now. So goddamn sick -- that was the greatest car I've ever had! And, now it's gone. Gone! Can't even get it back so I'm sick right now. I'm sick."

Cops confirmed the Lambo was eventually recovered in Maitland, Florida.

The good news ... Ross has reportedly made more than $67 mil during his NBA career ... so he'll be okay.

Plus, he's got insurance.