a) Co-worker is an asshole and who the hey knows what happened to your stuff but you can reach out and see if they maybe have it in a box somewhere. $12 will get you most smaller things shipped across America (pending you're here).
b) Idk where you sit on the whole retro-gaming thing. But they've got gobtones of little handheld systems that can emulate most older systems and they're loaded to the gils with games too. I don't have one (if I feel the spirit I emulate on my phone) but they look pretty nifty. I've actively looked at them and though "Hmm, that's pretty nifty!" I am just not sure how much I would play them, and I already do well enough with my phone.
c) On the tail-end - most people will be friendly first if you do reach out. They don't feel a bunch of shame about anything, especially if you were nice to them. They might just think about the good times you spent with them and reminisce. Seriously, I would consider reaching out and seeing whatsup and then ask them if they remember the DS. But also you clearly kissed it goodbye, so it is what it is. I hope you kick the tail outta the last bit of Sapphire some day =)