I am with BiancaStroud. I am a 'dog person', used to work with them until I had children and personally could never be without them as part of my family, but I would never judge someone like the OP for having made a very difficult decision that was in her judged opinion best for both her children and her dog.
None of us has enough information to judge how the rehoming was done and the OP reassured us that her dog is very happy and settled in its new home. Yes, its always sad when people have to rehome their pet, for whatever reason and its a shame that it ever has to happen, but sometimes there is just no alternative and we are lucky that dedicated people like Bianca and others involved in dog rehoming and rescue are there to help on these occasions.
Some people treat dogs as if they are possessions, some people beat and abuse them - but then some people do the same to children and other people. There are bad people in this world, plenty of them, for plenty of reasons - but its not right to rant and rail and treat every person that has to rehome their dog as if they are one of them.
I fail to see how all this dog-related ranting helps anyone, it just sets up a 'them and us' situation whereby there is always going to be a fight on every thread that so much as mentions dogs and in the process, stops people who genuinely need help and support with their dogs from asking questions of the very people who could help. As a 100% committed dog person, personally, I am sick of it.
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Now - back to the OP.
My ds1 has an incredible memory, he is 9, has AS and can clearly relate things that happened in his first year of life that I had completely forgotten about. He can also describe our first house in fine detail, despite the fact that we moved when he was 13 months old and he's never seen any photos of it and can talk confidently about the holiday we had travelling around the West Coast of Ireland for 6 weeks when he was 16 months old. However, if I ask him what happened at school today, or for example, on the sad occasions we have had to ask him to explain exactly what happened when he was bullied at school, he can't do it. He gets confused about what happened in what order and simply can't find the right words to explain.
He's also amazing at remembering facts and can relate facts he learned when he was pre-school age with ease, alongside all the new ones he loves cramming his brain with on a daily basis. He's a bit of a walking encyclopedia really! 
I suspect it has something to do with his AS related 'different wiring', in that his long term memory works really well, particularly with definite facts, but the part of his memory related to organisation, timescales and anything connected to emotions (eg the bullying) isn't as well connected and is therefore less efficient.