This is not to minimise your feelings for any of your clients, but if you came to know that one passed, what would you do?  Your place in his life makes it very difficult for you to mourn his passing in any visible way or to be of any consolation to his family.
As much as we may come to care about the people we see, both providers and clients, there is typically no room for each other in our private lives, or deaths...

Good question. I've been meaning to bring this up with a couple of ladies.

A few years ago I finally got my papers in order (will and the like) and one of the things I hope would happen is an email sent out to everyone in my address book summarizing that I have already caught the next bus and please don't reply to this email address.
 There are a few providers that are in my address book because we correspond.  They would hear that way.
 At least then people know what has happened and aren't left in mystery
 When I moved last year I made a point of goint to my regular 12 groups to tell folks I was moving so that nobody thought I had started abusing again.
 We do invest in each other, its part of what makes being human so great.
B

There is no way to know.

I know just what you mean "Sugar4kat."  I had a wonderful old guy I used to see, who would sometimes fly me around the country to meet him on business trips.  It was always a great time.

He was in his late 70's, and one day he just stopped answering e-mails and his phone was shut off.  I can only surmise that he passed on.

I still think of him on occasion.  But with no closure it leaves you wondering.  I guess liek you say, all we really have are the memories.

Hugs,
TS Jamie

...just as anyone else who knew the deceased can.

In fact, I joked to an ATF recently (I'm much older than she), "You'll be at my funeral." (I'll feeling great, BTW - was just making the point with her that I hope our relationship will endure.)

The question you ask, sugar4Kat, is a good practical one - How would you know?  There are two answers, one simple and one a little more personal.

The simple one is: read the obituaries every day, to see if you ever recognize a close client.

The more personal way is: ask your client if he has a friend or relative or executor who knows about his hobbying.  If so, ask him to give them your contact information "for any emergency".  This will have the benefit of letting him know that you care (when you feel that is appropriate).

In my opinion, professional boundaries do *not* exclude caring.  Wouldn't you expect his doctor and lawyer to be there at a client's wake or funeral, too?  If asked, you can invent some suitable white lie about how you knew each other.

I salute you, not only for your caring, but for your foresight and thoughtfulness.