The "America's Got Talent" alum tells us ... his beloved canine conjuror passed away on November 8th, just before his 17th birthday ... with Piff crediting the rescue dog for making his act sensational.

He adds ... "For over 15 years I’ve had the privilege and the pleasure of being upstaged and outshone night after night by Mr. Piffles. He came into my life when I had nothing, and set me on the path to a career I could only dream of. In the beginning, I may have rescued him, but in the end, he rescued me."

In the wake of the tragic update, the Flamingo Las Vegas -- where Piff and Mr. Piffles have had a fan-favorite residency for nearly a decade -- announced plans to throw a special ceremony in honor of the late dog.

The celebration will take place Wednesday evening, where the storied resort will unveil the Mr. Piffles Magical Playground ... a dog-friendly space dedicated to the Chihuahua.

Mr. Piffles' final show was supposed to be held today, on his 17th birthday.

Fans first became acquainted with Piff and his loyal companion when the pair appeared on season 10 of "America's Got Talent" ... where Piff boasted Mr. Piffles was the world's only magic-performing Chihuahua.

While Piff and Mr. Piffles didn't win the big prize, they did find themselves in the top 10 ... leading to their wildly successful Vegas residency.

Despite the loss of Mr. Piffles, Piff won't be hitting the stage alone ... as he previously cloned his longtime pet, shelling out a whopping $60K for Mr. Piffles the Second.