"We hope she's still out there and we just haven't found her yet," said Mark Hudson with the Fresno Police Department.
Thursday authorities turned their attention to a Central Fresno canal after a tip from neighbors who said they heard a possible drowning at the time of Lucy's disappearance.
"We've got detectives all along this route looking for any debris or anything of any evidence-- maybe some clothing we can associate to her that night," said Hudson.
But Thursday's search turned up empty, and Lucy's family remains hopeful.
Lucy's aunt, Mai Lor Xiong, said, "We want closure we want Lucy back-- waiting all morning these past days just waiting for this moment. In a way it's a relive but at the same time it's just the unknown."
Lucy's mother, Chao Yang, was the last to see her, when she walked out the gate of their apartment complex late last Thursday and never returned.
"These past days I haven't been able to eat. Whoever is out there, if you're harming her please let her go, as a mother I'm pleading to let my daughter back home."
Lucy's family suspects foul play, her aunt said she would never leave like this without saying anything.
"There's nothing like that with Lucy, she's just so focused on work and school. She has so many friends that love her, just something that was unseen that would happen," said Mai Lor.
Detectives are also looking at surveillance video after Lucy's credit card was used about a dozen times in the Tower District and in Madera following her disappearance.
Kor Xiong has been tethered to a bench outside his apartment since last Friday-- watching detectives as they scour the neighborhood, willing himself to believe his daughter will come home.
"You've been gone five days, I don't know where you are, I can't find you anywhere."
Kor last saw Lucy Friday morning; she had been out drinking with friends and came home late. When her mom confronted her Lucy ran away, and never came back.
"I can't eat, I can't sleep, and I not go to work. I don't know what to do, please come home."
Fresno detectives suspect foul play in Lucy's disappearance because of a phone call she made to her boyfriend. Police said she used an expletive and screamed right before the phone disconnected.
"I felt really uneasy, this isn't right, this isn't something she would do," said Andy Xiong, Lucy's brother.
Police believe Lucy may have been kidnapped and hope the individuals caught using her credit and debit cards may have answers. But they are also following up on a tip from neighbors who reported they saw a woman drowning.
"Right now the police are checking the canal, they thought it's you in the canal but I hope it's not you," said Kor.
Hoping instead Lucy is somewhere safe, watching, listening to her father's voice.
"If you see me, please come home, call me and your mom," said Kor.
We watched Tuesday morning as the Fresno Fire Department used a camera to search underwater-- but so far they've found nothing.
Over the next two days, the Irrigation District will be lowering water levels to allow for a more thorough search.