This is often the terribly heartbreaking price we pay for enjoying the love of a pet.... so sorry for your loss (((HUG!))) My Ike (R.I.P.) was a young guy when we had to put his buddy Nick down; the first night was awful because Ike insisted that we search everywhere to "find" Nick. But after that, he settled down; and was just glum for a few weeks.
Fast forward a decade - when it was time to send dear sweet Ike on that final trip, I wanted to avoid that "must find him at all cost" response from Jimmy and Jack. They were in the car when we went to the vet; and in a moment of clarity, I brought Ike's collar back with me to the car. I showed it to the 2 dogs, and between the empty collar and my clear grief, I think they understood that Ike wasn't coming home? Jack didn't seem to care; Jimmy needed a week or so of TLC (or else Jimmy sensed that *I* needed the TLC). At any rate, we made it through, and then puppy Ben came into our lives 8 weeks later and provided a delightful distraction.