I need An Excuse!!!?

I took my mom's phone (that she doesn't use) from her closet so that I could keep in touch with my bf. I had this gut feeling that she's been going through her things this past Saturday, and to my surprise, she was. She noticed that her phone wasn't there, and she knew that I had it somewhere (long story from the past), she has caught my chats before with him, and this time I made sure that every app I installed (Yahoo messenger) was uninstalled and all WiFi was disconnected. I cleared everything and returned it when she was in the bathroom. Now she knows I had it, and I'm stuck in a heavy situation, I need an excuse for taking the phone so that she doesn't go to his house to talk to his parents. I can't say it was for H.W of course cause I have other things to use for that like the laptop and iPad. Please help!! D: