Russell Simmons GF — Please Find My Dog! — ‘I’m FREAKING OUT!’

Exclusive 0913_Hana-Nitsche_russel_simmons_gettyRussell Simmons” girlfriend Hana Nitsche is heartbroken … and “freaking out” because her pet Chihuahua, Ivy, DISAPPEARED three days ago … and she”s hoping a HUGE reward — $5,000 — will help bring Ivy back.

Hana — a German fashion model — is plastering reward posters all over town … and bombarding social media with desperate appeals to find her dog — which vanished Tuesday near Doheny Drive in West Hollywood.

Her tweets have gotten increasingly frantic: “My heart is in so much pain!!” … “I”m really freaking out!!!” … “I”m really getting desperate.”

Russell has joined the search, too … posting Ivy”s pic and the reward offer on Twitter.

So, if you can read this Ivy … COME HOME!!!