So sorry, I can certainly relate to that.
We lost our Pom (shaddup). It was pretty much my daughter's dog and I have to admit, I did not pay a shit ton of attention to him because he was kind of annoying with his neediness. He had a cough that the vets basically called it "old man cough" whatever the fuck that was.
Then after about six months or so of that, my daughter found him dead when she came home from school.
Now he is gone, I see the little things he did every day that was part of my routine and I get sad when I turn the key in the lock and he's not losing his mind.