He bald-faced lied when he told everyone that he had a nightmare and felt so sad, he went for a walk in the middle of the night.
mcThinking: "I never was the best liar. Although, I seem to be getting better with all the lies I've had to tell lately."
mcThinking: "I guess that story will have to work. It's partially true. The nightmare was real, and I did drop my phone... somewhere."
mcThinking: "I have no idea what happened to my phone. How did that guy find it anyway? I looked everywhere."
mcThinking: "I better hurry up and call her..."
nar "*calls Tiffany*"
Tiffany: "[playerName]?!"
mc: "Tiffany, it's me. I'm fine."
Tiffany: "Oh thank god, you're okay. I was so worried about you!"
Tiffany: "Why didn't you go to school? And why didn't you tell me you weren't going?"
mc: "I had a terrible nightmare about Dad that put me in a sour mood, and I didn't want to go to school today. So I decided to go out and take a long walk in the woods and try to clear my mind."
mc: "I didn't want to wake you up this morning because I left very early, and by the time you were up, my phone stopped working."
mcThinking: "I hope she buys that. I hate lying to her, but there's no way she would believe the truth."
I understand the reason for his lies, and I assume either Skylar thinks the same way because she doesn't know the MC has also time traveled, or she can't tell him things for fear of "corrupting" the timeline just like Mystery Man, the redhead powerplant secretary, and presumably Riley.