Oh GetOnYourDancingShoes I am so sorry for your double loss . No person should ever have to go through what you have gone through...what you are, no doubt, still going through.
You are absolutely entitled to have one of 'those' moments, many of them in fact.
In regard to your question - I can only speak of my own experience - because my family and friends don't talk about my daughter who died, I find that I end up telling total strangers about her - from the girl at the check-out counter to the bin man, in fact, anyone who is willing to listen.
Whenever I am asked how many children I have, I always say 4 - if I then get asked how old they are, I say that my first child would have been 12 this year, but she died - I then tell them the ages of my 3 living children. Some people will enquire about the details of her death - the first question always being how old she was when she died - that irks me a bit, because I sometimes get the impression that when I say she died at 10 days, that they think 'oh OK, that's not so bad'. Others will not respond at all.
There is no right or wrong way to answer - personally I feel that I have a right to say that I have 4 children, because I did have 4 children - just because 1 of them is not around anymore, does not mean that she did not exist - but I sometimes shoot myself in the foot with that attitude, because I end up having to share very personal information with virtual strangers, because I basically volunteered the information first.
I don't know if I am making sense here .
PS: Your son may have physically died alone, but he died knowing that you loved him...your love was there with him - he was not alone.