Since 2 News began covering this story, investigators say they have received multiple calls about reported sightings of Zach Smith Sr.If this is your first time hearing of this story, here's some background: Mystery surrounding missing Sand Springs man continues to deepenHowever, those leads can be exhausting if they turn out not to be legitimate.2 News sat down with private investigator Eric Cullen to discuss any new updates in this case.He tells me they have received several tips to their company line, and while a tip is great, Cullen said proof of life is even better.What I would encourage the public to do is that if you think you have seen Zach Smith Sr. make sure and grab a photo or short video and pay attention to that left pinky. He doesnt have one from [the knuckle] up. Thats the best way someone could identify him, said Cullen.Investigators got a search warrant for Smiths car. However, Cullen said the data did not reveal anything significant.But then, on Dec. 15, a few more clues were discovered in this case.On Sunday night, late, Zach Smith Jr. found Zach Smith Sr.s phone, wallet, and key fob directly to the east of where the Corvette was found, said Cullen.We asked Cullen what he thought of this latest turn of events.He was moving around, so those are good signs, but anybody with any common sense would also know thats a little concerning because at this point, unless he had another phone, another means of payment, another means of identification, at this point his passport is missing, his wallets missing, his phone, his key fob, hes out of gas, its concerning for sure, said Cullen.If you see Zach Smith Sr. you are asked to contact the Osage County Sheriffs Office immediately.Stay in touch with us anytime, anywhere -- Download our free app for Apple, Android and Kindle devices. Sign up for daily newsletters emailed to you Like us on Facebook Follow us on Instagram SUBSCRIBE on YouTube