Savannah Guthrie Pleads for Nancy's Return in Mother's Day Post

This Mother's Day is a tough one for Savannah Guthrie ... she's spending it pleading for the return of her mother, Nancy.

She went on Instagram Sunday to share a touching tribute to her missing mom, posting a montage of cute clips but captioning it with a call for help.

Savannah wrote an emotional message to Nancy in the caption, saying ... "mother, daughter, sister, Nonie -- we miss you with every breath. We will never stop looking for you. We will never be at peace until we find you."

She continued by asking her followers to share anything they may know about her mother's disappearance, adding ... "We need help. Someone knows something that can make the difference. Call 1800CALLFBI. You can be anonymous and the reward remains available."

The caption concluded ... "Please keep praying. Bring her home." This comes just a few hours after her husband, Michael Feldman, shared a message of support.

Nancy's been missing since February 1 ... when she was taken from her Tucson, AZ home.

The Pima County Sheriff's Department has been leading the charge on the investigation and recently got some heat when they announced online, "Update: Nancy has been located."

This led the internet to believe Savannah's mom had finally been found ... but PCSD was talking about a different Nancy.