I am so sorry for your loss. Lewis must have been a kitty? I too lost my Mookie 2 weeks ago at 20 years old. She started to fade away quickly - i knew she was ill, but it just happened so quick.
Grief affects us all very differently. I have dreams about pets that have passed . In my dream, i go about a normal day - and my pet is always in my dream doing what it always did when it was here on earth. This just came to me, but maybe it is a sign from my deceased saying "I'm still there with you." ?? Could be, i don't know.
Just be sure to take the time to grieve. There are many stages you'll go through, but it just takes time.