According to her story, I count up three phones.
I take things for granted, like the police could see from records whether or not she actually did buy and use a third phone. It only says she had the third phone per her diary. If she'd only had two and the Helio hadn't been lost, at some point, she had to have another phone after she stashed the Helio in her grandfather's truck.
So maybe she never lost the Helio, it was the only phone she had on her trip. Once she got home, she hid the Helio, doctored her diary, and got another phone? A prepaid one like you can get at Walmart? I don't know. I'm assuming she had to have some phone and with a number that Freeman knew (because he called her the night of the body discovery. Unless she'd called him prior with this new number from the third phone).
It's very confusing to me, and I want proof of this third phone, basically.