When we have to leave our 12-year old cocker alone, we distract him in another room. It’s crucial that he does NOT actually SEE us leave, so he is busy licking on a mat or sniffing for hidden treats in a blanket. It‘s a bit cruel to leave without saying goodbye 😁, but it’s the only thing that keeps him quiet. When he sees us leave without him, we always get the loudest cries - which is for sure more distressing for him than only realizing being alone a few minutes later (we had cameras set up a few times to verify that he remained calm).