Why do you think he hid his cell or am i just imagining things?

So i was crusing with this guy that i have a thing with and when we were crusing his ex gf called when he saw she was calling he flipped his phone over so i believe becuz so i wouldnt know whos calling, when i left i text him and askd him why he did that but he said he didnt know what i was talking about that he wasnt hiding his cell, i just whatever then he text me and said who knows what she wants... what do you think? was he hiding it from me? If so why do yiou think he would do that?