I love how @sheldonia is totally wrong in her 'facts' about memory anyway. I'm sure other people have verified but I got derailed at her little tantrum. I have to know and do memory science research for my job, so anyone interested in the real science:
Memories are stored, but gradually fade and become more difficult to access as the neurological pathways leading to the memory get weaker if they're not recalled regularly. It's kind of like an actual path that no one walks anymore and becomes overgrown and inaccessible.
When you have an object, smell, location that is associated with just that memory, it's like a bulldozer clearing the path and allowing you full, easy, instant access again. Objects like the ones OP lost are the absolute strongest triggers that give access to the 'whole' memory again because of the powerful emotions attached to the object and the memory. The research on Flashbulb Memories and the developments since then support this.
So it's all very well saying, memories are in your head, what's the problem. But these objects allow you to relieve the memory as if it was happening again when you haven't seen them for a long time. You feel the same pride, joy, whatever, and it then can trigger other memories of that day.
The things OP lost are like time capsules. They're precious.
Not to mention that, due to the efficiency of our brains, we don't randomly recall past events unless they're directly relevant to the situation at hand. So while you might 'have' the memory in your head, your brain will never give it to you without a trigger. That could be someone saying, 'do you remember when DC made handprints at nursery' or you thinking about other DC 'firsts'.
In any case, if you're the sentimental switched-on type, you'll actively enjoy clearing that path with the bulldozer and relieving those moments again. Just because someone else doesn't 'get it', your DH or posters here don't get to dismiss your very valid feelings at having lost them. I'm very sorry 