Dead grandfather picked up the phone when I called my grandmother.

So I called my grandmother, like how I usually do from time to time. But when I called her up today, I don't think she picked it up. The line was silent for a while and then a guy, who sounded like my grandfather, said hello twice. I asked hi and who it is, and the line cut off.

I don't know how to feel about this. My grandmother told me that it is not showing that she picked the call. Same from my side, it shows more like she declined the call rather than talk to me for 5 seconds.

What I think makes me upset is that the experience wasn't a positive one. My grandfather means a lot to my family, but I held him in disdain since I felt like he could have been a better father to my mother and didn't mourn his death. His "Hello" didn't sound welcoming, it was a bit gruff and distant. More like, I'm just checking on you out of obligation.

What could I take away from this and what are the next steps?