What's the best excuse for not texting someone back in 2 days?

i haven't text a close friend who is a girl, and we are very close in 2 days, yes i've been ignoring her, but for a good reason and don't ask why, but she's been REALLY worried, keeps calling me i dont answer text me like 30 times i dont reply and finally i cant take it anymore and i need to talk to her again...once again dont ask why i did it, and dont tell me to tell her the real reason cause that wont be good...but whats a really good excuse if you want a "lie" for not talking to her in 2 days....grounding? lost phone? broke phone? i need some good ones