Wow Sneeky, I'm sorry, my condolences. It must have been shocking to receive those news over the phone all of a sudden. I mean, I'm always around my phone too, because I fear I miss a call from a relative outside the country (because I can't call back), but your case sounds a lot more extreme.
The best solution I think I can offer is for friends to call you (and you call them too of course), just to chat with them on friendly terms on the phone, making good things overwrite the bad, you know what I mean? right now your phone is full of bad vibes and you're scared of missing another call like that... maybe talking with friends over the phone will help diminish the importance of it and helping you relax more without it, because you'll trick yourself into thinking that even if you miss a call, it's no big deal, just someone who wanted to chat for a while.
I don't even know if that would work either, just an idea that I hope helps a bit at least and stressing over it would only hurt you (but we can't help but think about it, can't we?), I'm glad you reached out and that I was just glancing over my feed when I saw this!!!!